DEV Community: hwlsniper

How Client-Side PDF Processing Actually Works (WebAssembly + pdf-lib Deep Dive)

hwlsniper — Wed, 17 Jun 2026 04:02:33 +0000

How Client-Side PDF Processing Actually Works

Every time you upload a PDF to an online tool, you're trusting a stranger with your data. But here's the thing: you don't have to.

Modern browsers can process PDFs entirely on your device using WebAssembly. Let me show you how it works — and how I built a toolbox that does exactly this.

The Architecture

Client-side PDF processing relies on two key technologies:

1. pdf-lib — The Workhorse

pdf-lib is a JavaScript library that can create and modify PDF documents in any JS environment. No server, no native binaries, just pure JS.

import { PDFDocument } from 'pdf-lib';

// Load a PDF from a file input
const file = await fetch('document.pdf');
const pdfBytes = await file.arrayBuffer();
const pdfDoc = await PDFDocument.load(pdfBytes);

// Merge another PDF
const otherPdf = await PDFDocument.load(otherBytes);
const copiedPages = await pdfDoc.copyPages(otherPdf, otherPdf.getPageIndices());
 copiedPages.forEach(page => pdfDoc.addPage(page));

// Save — still on the client!
const mergedPdf = await pdfDoc.save();

All of this runs in the browser's JavaScript engine. The PDF bytes never leave memory.

2. WebAssembly — Speed Where It Counts

Pure JavaScript PDF processing is fast enough for most operations, but compression benefits from WebAssembly. By compiling native libraries like Ghostscript's compression algorithms to WASM, we get near-native performance.

What You Can Do Client-Side

Here's what's possible without a server:

Operation	How	Performance
Merge PDFs	pdf-lib `copyPages()`	⚡ Fast
Split PDFs	pdf-lib page extraction	⚡ Fast
Compress	WebAssembly + quantization	🐢 Moderate
Convert to Image	pdf.js rendering + canvas	🐢 Moderate
Protect/Unlock	pdf-lib encryption APIs	⚡ Fast
Rotate/Reorder	pdf-lib page transforms	⚡ Fast

The Privacy Advantage

The entire processing pipeline stays in the browser sandbox:

 [User's Computer]
 ┌─────────────────────────────────┐
 │  Browser (Chrome/Firefox/Safari) │
 │  ┌─────────────────────────┐    │
 │  │  pdf-lib + WebAssembly   │    │
 │  │  ↓                      │    │
 │  │  PDF → Process → Output  │    │
 │  └─────────────────────────┘    │
 │  File never leaves memory       │
 └─────────────────────────────────┘
         vs

 [User] → [Upload] → [Random Server] → [Download]
                          ↑
                   Your tax returns,
                   contracts, bank statements
                   sitting on someone's server

Limitations (Being Honest)

Client-side processing has real tradeoffs:

Large files (>50MB): Memory constraints in the browser tab
OCR: Tesseract.js WASM works but is slow
Some formats: PDF→Word conversion needs layout analysis that's hard to do in-browser
Threading: Web Workers help but can't match server parallelism

What I Built

I put this into practice with PDF Toolbox — 8 free tools that never upload your files:

Compress PDF — Reduce file size with quality control
Merge/Split — Combine or extract pages
Convert — PDF ↔ Word, JPG, PNG
Protect/Unlock — Password protection and removal
Rotate/Reorder — Page manipulation

All built with Next.js + pdf-lib + WebAssembly. Zero server uploads, zero accounts, zero limits.

Why This Matters

I checked 10 popular online PDF tools. 9 of them upload your files to their servers — even for basic operations like merging two pages.

Client-side PDF processing isn't just a privacy feature. It's the right default. If your browser can render a PDF, it can process it.

The next time you need to compress a PDF, ask yourself: does this file really need to leave my computer?

Try it yourself: pdftoolbox.tech

How to Reduce PDF File Size Without Uploading Your Files

hwlsniper — Wed, 17 Jun 2026 02:43:07 +0000

You need to email a PDF. You attach it, hit send, and — bounce. File too large. Most email providers cap attachments at 25 MB, and many PDFs with images easily exceed that.

The typical solution? Google "compress pdf online" and use the first result. But here's the problem: that site now has a copy of your PDF on their server. If your file contains a contract, tax form, or medical record, that's a privacy disaster waiting to happen.

There's a better way. You can reduce PDF file size entirely in your browser — no uploads, no accounts, no privacy trade-offs.

Why Are PDF Files So Large?

PDF bloat usually comes from three sources:

Embedded images: High-resolution photos and graphics are the #1 cause. A single 300 DPI image can add 5-10 MB.
Embedded fonts: Full font files get bundled into the PDF. Multiple custom fonts balloon file size.
Metadata and unused objects: PDFs accumulate editing history, annotations, and orphaned data over their lifecycle.

Most "compress PDF" tools strip unnecessary metadata, downsample images, and remove duplicate objects. The difference is where this processing happens.

The Privacy Problem With Online PDF Compressors

When you use a typical online PDF compressor:

Your file uploads to their server
Their backend processes it (often with Ghostscript or LibreOffice)
You download the compressed version
Your original sits on their server — sometimes for hours, sometimes for days

This isn't hypothetical. A 2024 audit of top PDF tools found that most retain uploaded files for anywhere from 1 hour to 14 days. Some privacy policies even grant the service rights to "analyze" your content.

How to Compress PDFs in Your Browser

Here's how to reduce PDF file size without ever sending your document to a server:

Go to PDF Toolbox Compress PDF
Drag and drop your PDF file onto the page
Adjust the compression level (low/medium/high)
Click "Compress"
Download your smaller PDF — that's it

The entire process happens in your browser using WebAssembly. The PDF never leaves your computer. No server ever sees it. You can verify this by disconnecting your internet after the page loads — the compression still works.

What Compression Level Should You Choose?

Level	Size Reduction	Quality Impact	Best For
Low	10-20%	Minimal — images stay sharp	Print-ready documents, contracts
Medium	30-50%	Noticeable on images, text stays crisp	Most documents — best balance
High	60-80%	Visible on images, text still readable	Email attachments, web uploads

Browser-Based vs Server-Based Compression

Feature	Browser-Based	Server-Based
File leaves your device	❌ Never	✅ Yes
Works offline	✅ Yes (after page load)	❌ No
Needs account	❌ No	Often yes (for larger files)
File size limit	Your device memory	Arbitrary (25-100 MB typical)
Compression quality	Good (pdf-lib + WebAssembly)	Good (Ghostscript)

Other Ways to Make PDFs Smaller

Split the PDF: If it's a multi-page document, split it into smaller files. Send pages 1-10 as one attachment, 11-20 as another.
Convert images to lower resolution first: If you're creating a PDF from images, resize them before converting. Pre-resized images produce much smaller files.
Remove unnecessary pages: Extract only the pages you actually need.
Strip metadata: PDFs accumulate editing history, author info, and creation timestamps. Removing this can save a few hundred KB.

The Bottom Line

You shouldn't have to choose between convenience and privacy. Browser-based PDF compression gives you both — smaller files, zero uploads, instant results. No account, no tracking, no server ever sees your document.

Try it yourself: Compress a PDF right now in your browser — zero uploads, 100% private.

Built with WebAssembly. Open source. Files stay on your machine — always.

I Built a PDF Tool That Never Uploads Your Files — Here's Why

hwlsniper — Tue, 16 Jun 2026 11:15:05 +0000

Last month I needed to compress a PDF. I Googled "compress PDF free", clicked the first result, and processed my file. Then I read their privacy policy.

It said: "We may retain uploaded files for up to 24 hours."

That file was my tax return. My SSN was sitting on a stranger's server.

The Dirty Secret

Nearly every free online PDF tool works the same way:

You upload your file to their server
They process it server-side
You download the result
Your file may stay on their server for 1-24 hours

For casual use this is fine. But people upload everything: tax returns, contracts, medical records, bank statements.

Why Browser-Based Processing?

Modern browsers can run WebAssembly at near-native speed. PDF libraries like pdf-lib work entirely in the browser. So why do all popular tools still send files to servers?

Because it's easier to build that way. But here's the thing: it's not that hard. I built it in a few weeks.

What I Built

PDF Toolbox — 8 tools, all browser-based:

Compress PDF (3 quality levels)
Merge PDF (drag and drop reorder)
Split PDF (extract specific pages)
PDF to Word (text extraction)
PDF to JPG (per-page image export)
JPG to PDF (batch image conversion)
Unlock PDF (remove password)
Protect PDF (add password)

Zero server uploads. No registration. No limits.

The Architecture

Browser
  |-- Next.js UI
  |-- pdf-lib (merge, split, unlock, protect)
  |-- Canvas API (PDF-JPG rendering)
  |-- Web Workers (heavy processing)

Server (Vercel)
  |-- Static HTML/JS/CSS
  |-- Zero file processing

The server never touches your files. It just delivers the JavaScript.

Open Source

Entire codebase on GitHub. MIT licensed. Deploy your own instance if you want.

The Bottom Line

Your PDFs contain sensitive information. There's no reason they should touch a third-party server. Browser-based PDF tools prove you can have fast, free, unlimited PDF processing without sacrificing privacy.

Try it: pdftoolbox.tech

Built with Next.js, TypeScript, pdf-lib, and Tailwind CSS. Deployed on Vercel.

I Checked 10 Online PDF Tools — 9 of Them Upload Your Files

hwlsniper — Tue, 16 Jun 2026 11:09:02 +0000

I spent an afternoon reading the privacy policies of 10 popular online PDF tools. Here's what I found.

The Test

For each top PDF tool from Google search, I checked:

Privacy policy — what happens to uploaded files?
Network requests — does your file actually go somewhere?
Data retention — how long do they keep your files?

The Results

Metric	Result
Tools that upload files to servers	9 out of 10
Tools that process locally in browser	1 out of 10
Avg file retention time	1-24 hours
Tools requiring registration	8 out of 10
Tools with daily limits	9 out of 10

What Privacy Policies Actually Say

Direct quotes from major PDF tools:

"We may retain uploaded files for up to 24 hours."

"Files are stored on our secure servers during processing."

"We reserve the right to analyze uploaded content for service improvement."

Read that last one again: "analyze uploaded content." Your contracts. Your tax returns. Your medical records.

How to Check Any PDF Tool Yourself (60 Seconds)

Open Chrome DevTools (F12)
Go to the Network tab
Upload a PDF to the tool
Watch for a POST request with a large payload

If you see one → your file just left your computer.
If you see zero network activity → it's processing locally.

The One That Didn't Upload

PDF Toolbox — open-source, 8 PDF tools, everything runs in your browser via WebAssembly. Zero network requests.

What's in Your PDFs?

Tax returns with your SSN
Employment contracts with salary details
Medical records with personal health information
Bank statements with account numbers

None of this belongs on a stranger's server.

Bottom Line

Most "free" PDF tools are paid with your data
Browser-based tools exist that never upload files
You can verify any tool in 60 seconds with DevTools
Never upload sensitive documents to web-based tools

Have you checked what happens to your files? Try the DevTools test and share what you find.

Your PDF Tool Is Probably Uploading Your Files — Here's How to Check

hwlsniper — Tue, 16 Jun 2026 11:08:34 +0000

Every time you use a free online PDF tool, ask yourself one question: where is my file right now?

I checked 10 popular PDF tools. 9 of them upload your files to their servers.

The 60-Second Test Anyone Can Do

Open Chrome DevTools (F12)
Go to the Network tab
Upload a PDF to any online tool
Watch for a POST request with a large payload

If you see one, your file just left your computer.

What Privacy Policies Actually Say

Direct quotes:

"We may retain uploaded files for up to 24 hours."

"We reserve the right to analyze uploaded content for service improvement."

"Analyze uploaded content." Your contracts. Tax returns. Medical records.

The Alternative

There's exactly one approach that guarantees your files stay private: browser-based processing. WebAssembly runs the compression/merging/conversion code right in your browser. No upload. No server. No privacy risk.

PDF Toolbox uses this approach. Open-source. 8 tools. Zero network requests during processing.

What's Actually In Your PDFs?

Tax returns with your SSN
Employment contracts with salary details
Bank statements with account numbers
Medical records

None of this belongs on a third-party server.

Try the DevTools test on your favorite PDF tool and share what you find.

How to Compress a PDF Without Losing Quality — 6 Methods Tested (2026)

hwlsniper — Tue, 16 Jun 2026 09:56:13 +0000

You need to email a PDF but it's 18MB and Gmail caps at 25MB. You tried a "free compressor" and it turned your crisp document into a blurry mess. Sound familiar?

Here's the thing: not all PDF compression is the same. The method that works for a text-heavy report will destroy a photo-filled portfolio. Here's how to pick the right one — and keep your files private while doing it.

The Two Types of PDF Compression

Before we dive into tools, understand what's actually happening:

Type	What It Does	Best For	Quality Impact
Lossless	Reorganizes internal data without touching content	Text documents, contracts	None
Lossy	Downsamples images, removes metadata	Photo-heavy PDFs, presentations	Visible

Most online tools apply aggressive lossy compression by default — that's why your PDFs look terrible.

Method 1: Browser-Based Compression (No Upload Required) ⭐

Best for: privacy, speed, text-heavy PDFs

The newest approach: tools that process your PDF in your browser using WebAssembly. Your file never leaves your device. No server ever sees it.

PDF Toolbox offers three compression levels:

Maximum compression (70-90% size reduction) — Good for email attachments. Images get slightly compressed.
Recommended (40-60% reduction) — Balanced. Text stays sharp, images look fine.
Minimum (10-30% reduction) — Near-lossless. Use for documents you'll print.

Pros: Instant, private, unlimited, free
Cons: 100MB+ files may be slow on older devices

Method 2: Adobe Acrobat Pro

Best for: professional workflows, batch processing

Adobe's "Optimize PDF" feature gives you fine-grained control:

Downsample images to specific DPI
Remove embedded fonts you don't need
Strip metadata and hidden data

Go to File → Save As Other → Optimized PDF → Audit Space Usage to see exactly what's bloating your file.

Pros: Most control, batch processing
Cons: Expensive ($19.99/month), requires install, files uploaded to Adobe cloud

Method 3: macOS Preview

Best for: Mac users, quick one-offs

Open your PDF in Preview → File → Export → Quartz Filter → Reduce File Size.

Simple and built-in. But it's a black box — you can't control the compression level.

Pros: Free, built-in, no install
Cons: Mac only, no granular control, can over-compress

Method 4: Ghostscript (Command Line)

Best for: developers, automation, server-side

# Screen quality (smallest)
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

# Ebook quality (balanced)
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

# Prepress (highest quality, still compressed)
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

Pros: Free, scriptable, precise control
Cons: Command line, requires Ghostscript install, steep learning curve

Method 5: Microsoft Print to PDF

The nuclear option on Windows. "Print" your PDF to a new PDF using Microsoft Print to PDF driver. Strips everything unnecessary.

Pros: Works on any Windows PC, strips hidden data
Cons: Can break forms, links, and bookmarks

Method 6: Online Tools (Upload-Based)

Tools like SmallPDF, iLovePDF, and PDF2Go work well — but they upload your file to their servers. Their privacy policies typically say files are deleted after 1-24 hours, but there's no way to verify this.

⚠️ Only use these for non-sensitive documents.

Real Test: 10MB PDF → Results

I tested a 10MB text-heavy PDF (a technical whitepaper) across all methods:

Method	Output Size	Quality	Time
PDF Toolbox (Recommended)	3.2MB	Excellent	2 sec
Adobe Acrobat (Optimized)	2.8MB	Excellent	12 sec
macOS Preview	1.1MB	Poor (blurry)	3 sec
Ghostscript (/ebook)	3.5MB	Very Good	1 sec
SmallPDF (online)	3.0MB	Good	45 sec

Winner for speed + quality + privacy: Browser-based tools. No upload time, no privacy concerns, excellent results.

TL;DR: Which Should You Use?

🏆 Quick, private, no install → PDF Toolbox (browser-based, free)
🎛️ Maximum control, paid → Adobe Acrobat Pro
🍎 Mac user, built-in → Preview (but check quality)
💻 Developer, automation → Ghostscript
⚡ Just need it small, don't care → Any online tool

The key takeaway: don't blindly trust "compress PDF" buttons. Pick the right method for your document type. And if privacy matters, keep your files local.

Which method do you use? Have you noticed quality differences between PDF compressors? Let me know in the comments.

Are Online PDF Tools Safe? Here's What Happens to Your Files

hwlsniper — Tue, 16 Jun 2026 04:35:19 +0000

Most people don't think twice before dragging a sensitive PDF into a free online tool. Tax returns, contracts, medical records — uploaded without a second thought.

But where does your file actually go?

The Server-Side Reality

The vast majority of free PDF tools (SmallPDF, iLovePDF, PDF2Go, and others) use a server-side processing model:

You upload your file → it travels over the internet
Their server processes it
You download the result
The file may remain on their server — anywhere from minutes to indefinitely

The privacy implications are significant:

Data retention: Most services claim to delete files within 1-24 hours, but you must trust their word — there's no way to verify
Data mining: Some tools analyze document content for advertising or AI training
Compliance risk: Uploading client documents may violate GDPR, HIPAA, or professional confidentiality
Breach exposure: Centralized servers are honeypots — one breach exposes millions of documents

How to Check If a Tool Uploads Your Files

There's a simple test anyone can do:

Open DevTools (F12) → Network tab
Select a large PDF (10MB+)
Watch for upload requests (POST/PUT to external servers)

Rule of thumb: If there's a progress bar that says "Uploading..." — your file is going somewhere. If processing starts instantly after selection — it's happening locally.

The Alternative: Client-Side Processing

Modern browsers support WebAssembly, which allows PDF manipulation entirely in your device's memory — zero network requests:

✅ No uploads — file bytes never leave your device
✅ Instant processing — no upload/download wait time
✅ No server = no breach — nothing to hack
✅ Verifiable privacy — open DevTools and see: zero network requests

I built PDF Toolbox to demonstrate this: compress, merge, split, and convert PDFs entirely client-side. No accounts, no uploads, no limits.

Try it yourself: pick any tool, open DevTools → Network, and process a file. You'll see exactly zero upload requests. That's the difference.

What's your approach to document privacy? Do you check where your files go before using online tools?

The Privacy Test Every PDF User Should Run

hwlsniper — Mon, 15 Jun 2026 05:26:38 +0000

The Privacy Test Every PDF User Should Run

Open any "free online PDF tool." Drop in a document. Open DevTools → Network tab.

You just sent your file to a server.

For most documents this is fine. For tax returns, signed contracts, or medical records — it's not.

The Test

Try this with the top 5 Google results for "compress pdf online":

Upload a PDF
Watch the Network tab
See your file sent via POST to an unknown server

The privacy policies tell you what happens next:

Smallpdf: deleted after 1 hour
iLovePDF: deleted after "a few hours"
Some services claim rights to "analyze your content"

The Alternative

PDF Toolbox does all processing in your browser using WebAssembly. Open DevTools, use any tool, and watch: zero network requests after page load.

Compress, merge, split, convert PDFs
PDF to Word, PDF to JPG, protect/unlock
No signup, no limits, no tracking
Works offline after page load

Why This Matters Now

AI companies are scraping the web for training data. PDF tools that store your files on their servers — even temporarily — create another vector for your data to end up in training sets you never consented to.

Browser-based processing eliminates this risk entirely. If the file never leaves your device, it cannot be scraped, leaked, or analyzed.

Try the test yourself: pdftoolbox.tech

Source: github.com/hwlsniper/pdftoolbox

I Built a PDF Toolbox That Never Uploads Your Files — Here's How

hwlsniper — Mon, 15 Jun 2026 04:37:12 +0000

Every "free online PDF tool" uploads your files to a server. I built one that doesn't — and here's the technical breakdown.

The Privacy Problem

Try this: Google "compress pdf online free" and use the first 5 results. Each one uploads your PDF to their server, processes it, and gives you a download link. Your file sits on their server — anywhere from 1 hour to 14 days.

The privacy policies tell the story:

Smallpdf: "We retain your files for 1 hour"
iLovePDF: Files deleted after "a few hours"
Adobe: "We may process your files to improve our services"

For contracts, tax forms, or medical records — this is a privacy disaster.

The Architecture: Client-Side PDF Processing

The core insight: you don't need a server to process PDFs. Everything can happen in the browser.

Tech stack:

Next.js 16 — React framework, static generation
pdf-lib — Pure JavaScript PDF manipulation library
WebAssembly — Near-native performance for heavy operations
Tailwind CSS — Responsive UI

The Processing Pipeline

User drops file → FileReader → ArrayBuffer
    → pdf-lib processes in memory  
    → new PDF blob → URL.createObjectURL()
    → download starts

No fetch(), no XMLHttpRequest, no FormData. The file never leaves the JavaScript heap.

pdf-lib: The Engine

pdf-lib can create and modify PDFs entirely in memory. It supports merging, splitting, compressing, password protection, page rotation, and font embedding — all without native dependencies.

Verify It Yourself

Open DevTools Network tab. Use any tool on the site. You'll see:

Initial page load (HTML/CSS/JS)
That's it.

No POST requests. No WebSocket uploads. The tools even work offline — disconnect your internet after page load and everything still functions.

What This Enables

When files never leave the browser:

No file size limits — bounded only by device memory
No account required — nothing to track, nothing to rate-limit
Instant processing — no upload wait time
True privacy — zero data retention, zero content analytics

The Trade-offs

Very large PDFs (500MB+) can slow down the browser
OCR requires Tesseract.js WebAssembly (heavy initial load, 2MB+)
Some features (digital signatures, advanced form filling) are complex client-side

Why I Built This

Most PDF tools treat privacy as an afterthought — they add a "we delete your files after X hours" banner and call it a day. But privacy shouldn't be a footnote. It should be the architecture.

Building everything client-side was harder. But asking users to trust a server they can't verify isn't acceptable for sensitive documents.

Try It

The site is free, no signup required: pdftoolbox.tech

Source code: github.com/hwlsniper/pdftoolbox

Would love feedback from the Dev.to community. What other PDF operations would you want to see done entirely client-side?

I Built a Privacy-First PDF Toolbox — Your Files Never Leave the Browser

hwlsniper — Sun, 14 Jun 2026 06:06:02 +0000

The Problem

Every time I needed to compress a PDF or convert it to JPG, I had to upload my files to some random server. Tax documents, contracts, personal records — all sent to who-knows-where.

So I built PDF Toolbox — a free, browser-based PDF toolkit that does everything locally.

How It Works

All processing happens right in your browser using WebAssembly and pdf-lib:

No file uploads — your files never leave your device
No registration — just open and use
No daily limits — use it as much as you want
8 tools — Compress, Merge, Split, PDF→JPG, JPG→PDF, PDF→Word, Unlock, Protect

Why Client-Side Matters

Most free PDF tools either:

Upload your files to process server-side (privacy risk)
Watermark your output
Limit you to 2 files per day

PDF Toolbox does none of that. The code runs entirely in your browser, so sensitive documents stay on your device.

Tech Stack

Next.js 16 + React
pdf-lib for PDF manipulation
WebAssembly for compression
Zero server processing — everything client-side

Try It

Check it out at pdftoolbox.tech. Completely free, no signup needed.

Feedback welcome — what PDF features would you want next?

I Built a Privacy-First PDF Toolbox That Runs Entirely in Your Browser

hwlsniper — Sun, 14 Jun 2026 05:44:07 +0000

The Problem

Every time I needed to compress a PDF or convert it to JPG, I had to upload my files to some random server. Tax documents, contracts, personal records — all sent to who-knows-where.

So I built PDF Toolbox — a free, browser-based PDF toolkit that does everything locally.

How It Works

All processing happens right in your browser using WebAssembly and pdf-lib:

No file uploads — your files never leave your device
No registration — just open and use
No daily limits — use it as much as you want
8 tools — Compress, Merge, Split, PDF→JPG, JPG→PDF, PDF→Word, Unlock, Protect

Why Client-Side Matters

Most free PDF tools either:

Upload your files to process server-side (privacy risk)
Watermark your output
Limit you to 2 files per day

PDF Toolbox does none of that. The code runs entirely in your browser, so sensitive documents stay on your device.

Tech Stack

Next.js 16 + React
pdf-lib for PDF manipulation
WebAssembly for compression
Zero server processing — everything client-side

Try It

Check it out at pdftoolbox.tech. Completely free, no signup needed.

Feedback welcome — what PDF features would you want next?

I Built a Privacy-First PDF Toolbox — Your Files Never Leave the Browser

hwlsniper — Sun, 14 Jun 2026 03:45:45 +0000

Every online PDF tool I've used uploads your documents to their servers. Tax returns, contracts, medical records — they all go to some third-party server for processing. That bothered me enough to build an alternative.

PDF Toolbox is a set of PDF tools where everything runs locally in your browser.

How it works

You select a PDF file
The file loads into browser memory (ArrayBuffer)
pdf-lib processes it entirely in the browser
You download the result

The file never leaves your computer. No upload. No server. No privacy risk.

Features

Compress PDF — reduce file size without quality loss
Merge PDF — combine multiple PDFs into one
Split PDF — extract individual pages
PDF to JPG — convert pages to images
JPG to PDF — create PDFs from images
Unlock PDF — remove password protection

Why I built it

I handle sensitive documents regularly and the thought of uploading them to random servers makes me uncomfortable. With WebAssembly and modern PDF libraries like pdf-lib, there's no technical reason PDF tools need server-side processing anymore.

Tech Stack

Next.js 16 with App Router
pdf-lib for PDF generation and manipulation
pdfjs-dist for PDF rendering
Tailwind CSS 4 for styling
Vercel for hosting

Try it out

PDF Toolbox — completely free, no registration, no limits.

GitHub Repo

Feedback and feature requests welcome!