DEV Community: At Use

Free CSV to JSON and JSON to CSV Converters - at-use.com

At Use — Tue, 14 Jul 2026 06:34:19 +0000

Two new free developer tools just went live on at-use.com:

CSV to JSON Converter

Paste or upload a CSV file (up to 20 MB) and get JSON out in the format you actually need:

Array of Objects - {"name":"Alice","age":30}
Array of Arrays - [["Alice",30]]
Keyed JSON - first column as key: {"Alice":{"age":30}}
JSONLines/NDJSON - one object per line

Auto-detects delimiter (comma, tab, semicolon, pipe). Handles quoted fields, embedded newlines, unicode. Server-side PHP, nothing stored.

JSON to CSV Converter

Paste a JSON array and download a CSV:

Supports Array of Objects, Array of Arrays, JSONLines
Flattens nested objects to dot-notation columns (ddress.city)
Custom delimiter, quote character, header row toggle
Preview first 10 rows; full file available via download

Server-side, nothing stored.

Both tools are free, no sign-up required.

YAML to JSON and CSS Formatter - now with Google rich results schema

At Use — Mon, 13 Jul 2026 09:06:53 +0000

Two free browser tools now qualify for Google's rich results: YAML to JSON Converter and CSS Formatter.

Both have full structured data: SoftwareApplication, FAQPage, HowTo, and BreadcrumbList. That's what generates the Q&A panels and step-by-step guides you see above the regular search result link.

What each tool does

YAML to JSON: paste your config, get JSON output. Handles multi-document YAML (the --- separator), Kubernetes manifests, Ansible playbooks, Helm charts. Server-side processing, nothing stored.

CSS Formatter: format, beautify, minify, and validate CSS in one place. Syntax errors report line and column numbers.

Both are free. No signup. No install required.

Free image optimizer with batch resize, 50+ formats, and no account needed

At Use — Wed, 08 Jul 2026 08:07:42 +0000

The image optimizer at AT USE handles the formats you actually use - JPG, PNG, WEBP, AVIF, BMP, TIFF, HEIC, and 50+ more - in a batch. Upload multiple images, pick a preset or enter custom dimensions, download a ZIP.

What it does

Crop, resize, compress to any pixel dimension
Social-media presets (Instagram square, Twitter/X header, LinkedIn banner, YouTube thumbnail)
Batch ZIP download - resize 20 images, get one file
20 MB per file limit

How it works

Images go to the server (ImageMagick), get processed, come back. No browser-based canvas API. HEIC files work, AVIF output is real, results are consistent across every device and browser.

What it doesn't do

No account. No watermark. No stored history after the session ends.

Free at: https://at-use.com/tools/image-optimizer/

16 Free Online Developer Tools - No Signup, No Install (2026)

At Use — Sun, 28 Jun 2026 15:47:52 +0000

Most developer tool roundups link to GitHub repos you have to run locally, or to SaaS products that require an account and an email confirmation before you can do anything.

Here are 16 browser-based tools on AT USE that work immediately - paste or type, get the result. Free, no registration, no install.

Encoding & Decoding

Base64 Encoder/Decoder - Encode strings or files (including images) to Base64, or decode Base64 to text/data URI. Supports file upload up to 5 MB with live image preview.
URL Encoder/Decoder - Percent-encode any string, or decode URL-encoded text. Useful for building query strings, debugging redirect chains, and testing API endpoints.
HTML Entity Encoder/Decoder - Convert special characters to HTML entities and back. Both named entities (&) and numeric (&) output modes.
Binary Translator - Convert text to binary and binary to text. Includes hex and decimal modes.

JSON & Text

JSON Formatter/Validator - Paste JSON to format, validate, and highlight syntax errors. Shows the error line and column if malformed.
JWT Decoder - Decode any JWT token to read header, payload, and expiry. Does not verify signatures - use for inspection, not validation.
Text Diff - Paste two blocks of text to see a line-by-line diff. Highlights added, removed, and changed lines.
Case Converter - Convert text between camelCase, snake_case, PascalCase, kebab-case, CONSTANT_CASE, and 8 other formats.
Markdown to HTML - Convert Markdown (GitHub Flavored) to clean HTML. Supports tables, strikethrough, task lists. Uses marked.js; runs entirely in the browser.
Code to Image - Screenshot any code snippet as a PNG. Choose theme, language, font size, and padding. Useful for LinkedIn posts, slides, or READMEs where you want syntax-highlighted code without a screenshot tool.

Regex, Security & Generators

Regex Tester - Test regular expressions against sample text. Shows all matches highlighted in real time. Supports flags (global, case-insensitive, multiline, dotall).
Hash Generator - Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text input.
UUID Generator - Generate UUID v4 (random), v1 (timestamp), or nil. Generate in bulk or one at a time.
Password Generator - Generate passwords with configurable length and character sets (uppercase, lowercase, digits, symbols).

Time, Date & Scheduling

Unix Timestamp Converter - Convert Unix timestamps to human-readable dates and vice versa. Shows UTC and local time. Works in milliseconds and seconds.
Cron Expression Builder - Build and validate cron expressions with a visual UI. Shows the next 5 scheduled run times. Supports standard 5-field and extended 6-field (with seconds) formats.
Timezone Converter - Convert a time between any two time zones. Supports all IANA time zones with UTC offset and DST awareness.
Number Base Converter - Convert numbers between decimal, binary, octal, and hexadecimal.

All tools are free, server-side (for processing) or browser-side (for analysis), with files deleted after download on any tool that accepts uploads. No account, no tracking beyond standard analytics.

The full set is at at-use.com/tools/developer.

Free TinyPNG Alternative That Supports AVIF, HEIC, and WEBP

At Use — Wed, 24 Jun 2026 12:20:18 +0000

Stop Paying for Image Compression

Most developers reach for TinyPNG out of habit. It works — but it only compresses JPEG and PNG, and cannot output modern formats like AVIF or WEBP.

AT USE Compress Image is a free, server-side alternative that handles six formats.

What It Supports

Input: JPEG, PNG, WEBP, AVIF, HEIC (iPhone photos), TIFF
Output: JPEG, PNG, WEBP, AVIF, BMP, TIFF
Quality slider: 1 to 100 for fine-grained file size control
Metadata strip: removes EXIF data before sharing
Server-side processing via ImageMagick — handles HEIC natively

Where TinyPNG Falls Short

TinyPNG cannot output AVIF or WEBP. AVIF achieves 30 to 60% smaller file sizes than JPEG at equivalent visual quality, with broad browser support since Safari 16.4.

How It Works

Upload your image (up to 20 MB)
Set your quality target
Pick the output format
Download — the file is deleted from the server after download

Nothing is stored. No account required.

When to Use It

Compressing product images before uploading to a CMS
Converting iPhone HEIC photos to web-safe JPEG or WEBP
Generating AVIF variants for picture elements in your HTML
Stripping EXIF location data before posting images publicly

at-use.com/tools/compress-image

Part of AT USE, a free toolbox for creators, marketers, and developers. No login required.

30 Free Online Developer Tools - No Signup, No Install (2026)

At Use — Tue, 23 Jun 2026 11:53:34 +0000

26 Free Online Developer Tools - No Signup, No Install (2026)

Every developer has a graveyard of browser bookmarks for tools used once every few months: a JWT decoder, a cron expression validator, a DNS checker. The problem with most of these tools is they require creating an account, installing an extension, or pasting data into a site that could be logging everything you send.

I have been using at-use.com as my go-to bookmark for exactly this reason. It is a collection of 30+ browser-based tools that run in the browser or server-side (for network lookups), no account required. Here is a rundown of the ones I actually use.

Encoding & Decoding

Base64 Encoder/Decoder

Paste in text or a binary string, get Base64 out. Or the reverse. Handles URL-safe Base64 variants too. Useful for decoding config file values, JWT payloads, or any API response that came back encoded.

URL Encoder/Decoder

Encodes special characters for query strings or decodes a percent-encoded URL into something readable. Faster than decodeURIComponent() in the browser console when you are debugging a broken redirect.

HTML Entity Encoder

Two modes: HTML-safe (encodes <, >, &, ", ') and all-non-ASCII (encodes every character above codepoint 127). Useful when you need to embed user-generated content in HTML without running a full sanitization library.

Binary Translator

Converts text to binary and back. Also handles hex and decimal. The BigInt implementation handles 64-bit values without precision loss, which matters when debugging numeric IDs from databases that use bigint columns.

Text & Code

JSON Formatter

Paste in minified JSON, get pretty-printed output with syntax highlighting. Validates and shows the exact line/character of any parse errors. I use this constantly when logging API responses as single-line strings.

Markdown to HTML

Live split-panel preview. Renders GFM: tables, task lists, fenced code blocks, strikethrough. Outputs clean HTML you can copy or download as a .html file.

Text Diff

Paste two versions of a string and see a character-level diff. Useful when you need to spot the difference between two similar error messages or config values without setting up a full diff tool.

Case Converter

camelCase to snake_case to PascalCase to kebab-case to SCREAMING_SNAKE_CASE. Handles Unicode correctly, not just ASCII.

Regex Tester

Live regex testing with match highlighting. Supports flags (global, case-insensitive, multiline, dotAll). Shows match groups and capture groups separately.

Readability Checker

Runs Flesch-Kincaid, Gunning Fog, and a few other readability scores against a block of text. Useful for technical writing - especially when checking that documentation is at the right reading level.

Security & Authentication

JWT Decoder

Paste in a JWT, get the header and payload decoded. No verification (client-side decoder, not a validator), but useful for inspecting token contents during debugging without sharing the token with any external service.

Hash Generator

MD5, SHA-1, SHA-256, SHA-512. Paste text, get the hash. Good for quickly verifying checksums or confirming that two strings produce the same hash.

Password Generator

Configurable length, character sets (uppercase, lowercase, numbers, symbols), excludes ambiguous characters by default. All generation happens client-side.

Time, Date & Scheduling

Unix Timestamp Converter

Converts between Unix timestamps and human-readable dates. Handles milliseconds. Shows results in multiple timezones simultaneously - useful when looking at API logs that store timestamps in UTC while you are somewhere else.

Cron Expression Builder

Visual builder for cron expressions: click through minute/hour/day/month/weekday fields. Includes a parser that takes any cron expression and outputs a plain-English description. Shows next 5 scheduled run times with UTC/Local toggle.

Network & DNS

DNS Lookup

A/AAAA/CNAME/MX/TXT/NS records for any domain. Server-side lookup, so you see what is actually propagated, not what is cached on your local resolver.

WHOIS Lookup

Full WHOIS data for any domain. Useful for checking registration dates, nameserver assignments, or registrar details.

CNAME Lookup

Resolves CNAME chains end-to-end. Helpful when debugging CDN configurations or alias records that chain through multiple levels.

MX Lookup

Lists MX records with priorities. Good for checking email routing or verifying that custom domain email is correctly pointed.

SPF & DMARC Checker

Parses SPF records and DMARC policies, flags common misconfigurations (overly broad +all, missing p=reject in DMARC). Practical for debugging deliverability issues.

SSL Checker

Shows certificate chain, expiry dates, issuer, and Subject Alternative Names. Flags common issues like mismatched common name or incomplete chain. Useful before deploying a cert or checking a third-party domain.

HTTP Headers Checker

Fetches and displays response headers for any URL. Shows redirect chains up to 5 hops. Highlights security headers - HSTS, CSP, X-Frame-Options, X-Content-Type-Options - and flags which are missing.

Online Status Checker

Checks if a URL is reachable from the server, bypassing your local network. Useful when unsure if a service is down for everyone or just your connection.

Generators & Utilities

UUID Generator

Generates UUID v4 (random). Client-side, uses crypto.randomUUID(). Generates a batch at once if you need multiple.

Number Base Converter

Converts between binary, decimal, hex, and octal. Uses BigInt for 64-bit values. Includes a two's complement viewer with configurable bit width (8/16/32/64-bit) for debugging signed integer representations.

Code to Image

Takes a block of code and renders it as a shareable PNG with syntax highlighting and a clean background. Useful for documentation, presentations, or posts where you want to show a code snippet without a raw screenshot.

JSON Diff Checker

Paste two JSON objects and see exactly what changed - additions highlighted in green, removals in red, with side-by-side and unified diff modes. Supports key-order sensitivity toggle and hiding unchanged content. Server-side processing, 1 MB per pane limit.

Color Picker from Image

Upload any image and click anywhere on it to extract the exact HEX, RGB, and HSL color codes at that pixel. Useful for pulling brand colors from logos or screenshots without loading a full design tool.

Text Diff Checker

Line-by-line comparison of two text blocks. Returns a unified diff with added/removed/unchanged stats and similarity percentage. Handles large pastes without client-side memory limits.

Unix Timestamp Converter

Bidirectional epoch time conversion - paste a 10-digit (seconds) or 13-digit (milliseconds) timestamp to get a human-readable date, or enter a date to get the epoch. Auto-detects seconds vs milliseconds.

What is missing

No API testing interface, no SQL formatter, no container tooling. Now at 30 tools. For standalone lookup and conversion tasks it covers the common ground well, without requiring an account or sending your data to a third party.

The developer tools hub groups everything above in one place. The network DNS hub has the full set of network tools.

26 Free Online Developer Tools — No Signup, No Install (2026)

At Use — Tue, 23 Jun 2026 06:50:03 +0000

Most "free developer tools" lists link to GitHub repos you need Node.js to run locally, or SaaS products with a login wall. Everything below runs in a browser tab, handles your data client-side or deletes it from the server within 30 minutes, and requires no account of any kind.

All 26 tools are at at-use.com. Grouped by what you are actually trying to do.

Encoding & Decoding

Base64 Encoder/Decoder â€” Encode text or binary to Base64, or decode it back. UTF-8 text and binary file payloads both work. Runs in your browser â€” nothing sent to a server.

URL Encoder/Decoder â€” Percent-encode strings for safe URL inclusion, or decode percent-encoded URLs back to readable text. Handles both application/x-www-form-urlencoded and RFC 3986 encoding modes.

HTML Entity Encoder/Decoder â€” Convert special characters to named HTML entities (< â†’ <, & â†’ &) or decode entities back to characters. Useful when building template strings or sanitizing output for display.

Binary Translator â€” Text to binary, binary to text, or translate between binary, decimal, hex, and octal. Useful for low-level debugging and learning number representations.

Number Base Converter â€” Convert integers between binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16). All four outputs shown simultaneously.

JWT Decoder â€” Paste a JWT token to decode and inspect the header and payload. Runs entirely in the browser â€” your token never leaves your machine.

JSON & Text

JSON Formatter & Validator â€” Format, validate, and minify JSON in one click. Toggle between pretty-print and compact output. Syntax errors include the exact line and column number. Uses browser-native JSON.parse() â€” no data sent anywhere.

Text Diff â€” Side-by-side text comparison with no character limit (diffchecker.com caps at 25,000 characters on the free tier). JSON-aware mode auto-formats both inputs before diffing so whitespace differences do not pollute the output.

Case Converter â€” 12 text case formats at once: camelCase, PascalCase, snake_case, kebab-case, SCREAMING_SNAKE, Title Case, dot.case, and more. All outputs update as you type â€” paste once, copy whichever format you need.

Markdown to HTML â€” Convert Markdown to HTML with syntax highlighting for code blocks. Side-by-side preview. Clean semantic output, no inline styles.

Regex Tester â€” Test regular expressions against sample text with real-time match highlighting. Flags (global, case-insensitive, multiline, dotAll) can be toggled. Match groups are listed below the input.

Readability Checker â€” Flesch-Kincaid Grade Level, Flesch Reading Ease, Gunning Fog Index, and Automated Readability Index. Handy for checking whether your documentation or API reference copy is accessible to a broad audience.

Time & Date

Unix Timestamp Converter â€” Convert between Unix timestamps and human-readable dates. Handles both seconds and milliseconds. Shows UTC, your local timezone, and ISO 8601 format simultaneously.

Cron Expression Builder â€” Build and validate cron expressions with a visual UI. Shows the next 5 scheduled run times so you can confirm the schedule is correct before deploying.

Generators

UUID Generator â€” UUID v1, v4, or v7 in bulk. Set the count (1â€“1000), generate, copy or download as a plain text list. Browser-side only â€” no server involved.

Hash Generator â€” MD5, SHA-1, SHA-256, SHA-512 from text input or file upload. Runs in the browser using the Web Crypto API. Results copy in one click.

Password Generator â€” Configurable length, character sets (uppercase, lowercase, numbers, symbols), exclusion of ambiguous characters. Generate multiple passwords in one batch.

QR Code Generator â€” Enter any URL or text string and download a QR code as PNG or SVG. No account, no watermark.

QR Code Reader â€” Upload a QR code image or use your camera to scan one. Decoded entirely in the browser â€” nothing sent to a server.

Barcode Generator â€” Code 128 (alphanumeric), EAN-13 (international retail), UPC-A (US retail), and Code 39 (industrial/logistics) formats. PNG or print-ready SVG output.

Network & DNS

DNS Lookup â€” Query A, AAAA, CNAME, MX, TXT, NS, SOA, and PTR records for any domain.

WHOIS Lookup â€” Registration info, nameservers, registrar, and status for any domain.

HTTP Headers Checker â€” Inspect the HTTP response headers returned by any URL. Useful for debugging caching policies, CORS configuration, content-type, security headers (HSTS, CSP, X-Frame-Options), and redirect chains.

Subnet Calculator â€” CIDR to subnet breakdown: subnet mask, wildcard mask, broadcast address, usable host range, and binary representation. Supports IPv4 and IPv6.

Email & Deliverability

SPF Checker â€” Validate your SPF record, check alignment, and see a pass/fail result for a given sending domain.

DMARC Checker + DKIM Lookup + SSL Checker + BIMI Checker â€” The SPF tool links to all four of these, so you can step through the full email authentication audit in one go: DMARC policy, DKIM key existence, SSL certificate chain, and BIMI logo record. Five tools covering the whole stack.

The trade-off

The site is ad-supported. That is the trade: you see an ad, you get the tool, no account needed, no data stored beyond what is needed to process your file (and that is deleted within 30 minutes). Encoding and generator tools never touch a server at all.

Developer tools hub: at-use.com/tools/developer
Network/DNS tools hub: at-use.com/tools/network-dns

Free SSL Certificate Checker — verify expiry, issuer, and chain for any domain

At Use — Fri, 19 Jun 2026 15:48:04 +0000

Dealing with a browser security warning on a site you manage? Not sure when a Let's Encrypt cert auto-renews? Need to verify the certificate chain is complete after deploying a new bundle?

I built a free browser-based tool for this: SSL Certificate Checker.

What it checks

Enter any domain (example.com or paste a full URL) and the tool does a live TLS handshake from the server. You get:

Status — Valid ✓, Expired ✗, or Not Found ✗
Expiry countdown — exact date + days remaining (warns at ≤30 days, urgent at ≤14)
Issuer — Let's Encrypt, DigiCert, Sectigo, etc.
Key algorithm — RSA 2048-bit, EC 256-bit, etc.
Subject Alternative Names — up to 5 SANs shown + overflow count
Certificate chain — Complete ✓ or Incomplete ⚠

When to use it

Before a site launch — confirm HTTPS is correctly set up
Browser shows "Your connection is not private" — get the exact reason
Let's Encrypt auto-renewal isn't working (Certbot sometimes fails silently)
NET::ERR_CERT_AUTHORITY_INVALID — often a missing intermediate CA in the chain
Check SAN coverage across a multi-domain or wildcard cert

How it works

Server-side PHP uses stream_socket_client to connect to {domain}:443, captures the certificate and chain via SSL context, then parses with openssl_x509_parse(). Rate-limited at 5 checks per minute per IP. No data is logged.

Free, no account required: at-use.com/tools/ssl-checker