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Rashid Salimov
Rashid Salimov

Posted on Originally published at vault-pro.rashid-salimov96.workers.dev

10 Essential Free Developer Tools That Run 100% In-Browser (Zero Server Upload)

Have you ever needed to format a production SQL query containing customer records, parse a cURL command with an active Authorization: Bearer secret, or convert sensitive JSON data to TypeScript types?

Most online formatters and conversion tools send your clipboard content to remote backend servers. If their servers are compromised, log incoming requests, or use third-party analytics, your internal tokens and database schemas are exposed.

To solve this, Digital Vault PRO is an open, client-side utility suite built on Astro 5, WebAssembly, and the Web Crypto API. 100% of calculations execute locally in your browser — zero bytes are ever uploaded to any server.

Here are 10 of the most practical tools available for daily engineering workflows:


1. cURL to Code Converter

Quickly transform complex curl requests with headers, multi-line arguments, and JSON payloads into clean, idiomatic code for:

  • JavaScript fetch() (async/await)
  • Python requests
  • Go http.NewRequest
  • PHP curl_init

It parses quotes and multi-line arguments locally without sending your auth headers across the wire.


2. Docker Run to Docker Compose Converter

Paste one or multiple docker run -d --name app -p 8080:80 -v /data:/var/www -e ENV=prod nginx:alpine commands and instantly generate a standardized docker-compose.yml file with port mappings, volume definitions, environment arrays, and restart policies.


3. JSON to TypeScript Interface Generator

Paste raw API responses or nested JSON objects. The engine infers types, generates clean PascalCase TypeScript interfaces, detects optional properties, and handles recursive structures.


4. CSV to SQL INSERT Query Generator

Convert spreadsheet CSV exports into batch INSERT INTO table (...) VALUES (...) statements:

  • Automatically infers integers, floating-point numbers, booleans, and SQL NULL
  • Escapes special characters
  • Supports PostgreSQL, MySQL, and MS SQL dialects in batches of 50 rows

5. Linux Chmod Permissions Calculator

Visual matrix toggles for Read (r), Write (w), and Execute (x) permissions across Owner, Group, and Public tiers. Generates octal numbers (e.g., 755, 644) and symbolic strings (rwxr-xr-x) on the fly.


6. IPv4 CIDR Subnet Calculator

Calculate network address, broadcast address, netmask, wildcard mask, usable host IP ranges, and total address counts for subnets ranging from /1 to /32.


7. Client-Side Diff Checker

Side-by-side and inline syntax difference viewer using Myers diff algorithm. Compare source code, configuration files, and SQL schemas with zero server involvement.


8. Visual Cron Expression Generator

Visually configure cron intervals (minute, hour, day, month, weekday), view human-readable explanations in plain English, and calculate the next 5 execution timestamps.


9. Aspect Ratio & Resolution Calculator

Compute greatest common divisors (GCD), identify standard aspect ratios (16:9, 4:3, 21:9, 9:16), and scale dimensions without distorting images or videos.


10. Client-Side Word & Keyword Frequency Analyzer

Analyze texts and markdown articles: unigrams, bigrams, trigrams, reading time, character counts, and keyword density — ideal for SEO and documentation polish.


Privacy and Self-Hosting

  • Live web app: vault-pro.rashid-salimov96.workers.dev
  • Bilingual: English & Russian (/en/ and /)
  • Self-hosting: The entire project can be hosted locally via an Alpine Nginx Docker container (~15MB) with zero cloud dependencies.

Bookmark it, keep your API secrets safe, and let me know in the comments which developer utility you would like to see added next!

Top comments (1)

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Maame Afua A. P. Fordjour •

The chmod calculator is the one for me! I’m learning Linux and I still have to stop and think every time I see 755 or 644 šŸ˜… Being able to toggle it visually and see the octal and rwx side by side makes it click so much faster. Bookmarked!