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Developer Tools

Q: How do I compare two config files without scrolling back and forth?

Use Text Diff . Paste the old version on the left and the new version on the right; the tool highlights line-by-line differences so you can confirm only the intended lines changed before deploying.

Use these developer tools to inspect, minify, compare, and transform code or text directly in your browser.

JSON Parser & Formatter (Tree View)
Paste JSON to validate, format, and view it in a tree.
CSS Minifier Online - Free, Paste & Minify Instantly
Minify CSS online for faster page loads.
CSS Unminifier Online - Beautify Minified CSS Free
CSS unminifier online - beautify minified CSS with proper indentation, line breaks, and readable formatting.
JavaScript Minifier Online - Free, Paste & Minify JS
JavaScript minifier online free - paste your JS, click Minify, and copy the compressed code.
JavaScript Unminifier - Beautify Minified JS Online
JavaScript unminifier online - reformat minified JS with indentation and line breaks for stack-trace debugging.
Text Diff Checker Online - Compare Text Side-by-Side
Text diff online - compare two text blocks and highlight added, removed, and changed characters, words, or lines.
MD5 Hash Generator (Text to MD5, Free)
Free online MD5 hash generator and MD5-to-text reverse lookup.
CSS Gradient Generator - Build & Copy Gradient Code
CSS gradient generator - build animated linear gradients with live preview; copy ready-to-paste CSS with vendor-prefix fallbacks for every browser.
Text to HTML Editor Online - Live WYSIWYG Preview
Text to HTML editor online - write in a WYSIWYG view and watch the generated HTML update live, with JavaScript support.
Online Regex Tester - Match, Highlight and Debug Patterns
Regex Tester Online - Test a regular expression against your own sample text and watch every match highlight as you type.
Color Picker - Free Online, No Sign-Up
Pick a color and read its HEX, RGB, and HSL values, with complementary, analogous, and shade palettes and one-click copy.
Data Visualizer - Free Online, No Sign-Up
Paste CSV, JSON, or Label, Value rows and draw them as bar, line, pie, and more chart types - all in your browser.
Online Code Editor - In Your Browser, No Upload
A free in-browser code editor powered by the Monaco engine behind VS Code.
Code Beautifier - Format JavaScript, CSS & HTML Online
Beautify JavaScript, CSS, HTML, and JSON in your browser.
Word Counter - Count Words, Characters & Reading Time
Count words, characters, sentences, lines, and estimated reading time live as you type or paste text - free, in your browser, no upload.
Sort Text Lines Online - Alphabetize a List A-Z or Z-A
Free online tool to sort text lines alphabetically, A-Z or Z-A, right in your browser.
Remove Duplicate Lines Online - Keep the First, Drop the Repeats
Free online tool to remove duplicate lines from a pasted list, right in your browser.
Reverse Text Online - Flip a String Character by Character
Free online tool to reverse a block of text character by character, right in your browser.
Text Repeater - Repeat Text Online, Free
Free online text repeater.
Base64 Encoder and Decoder - Text to Base64 in Your Browser
Encode text to Base64 or decode a Base64 string back to text, right in your browser - no upload and no account.
URL Decoder Online - Free Tool
URL Decoder - Free Online Tool.

Common developer workflows

Inspect API responses: Parse JSON into a readable tree view.
Optimize assets: Minify CSS or JavaScript before publishing.
Debug minified files: Unminify code to track down issues.
Compare revisions: Use text diff to check changes line by line.
Generate identifiers: Create MD5 hashes for quick checksums.

Three steps to pick a developer tool: name the task, open the matching tool, then run it in your browser. — Common developer workflows start with the task - inspect an API response, optimize assets, or debug a minified bundle - then reframe it as the matching child tool and run it in your browser.

Which tool to use, by task

JSON Parser to validate and explore complex payloads.
CSS Minifier or JS Minifier to shrink assets for production.
CSS UnMinifier or JS UnMinifier to make code readable again.
Text Diff for quick comparisons between versions.
MD5 Converter to generate hashes from text strings - use it for integrity checks, not password storage.
Regex Tester to match a pattern against sample text live, with per-group highlights and flag toggles (g, i, m, s, u, y).
CSS Gradient Generator to build reusable gradient styles.
Text To HTML Editor when you need simple markup quickly.
Color Picker to grab a HEX, RGB, or HSL value for a design.
Data Visualizer to turn rows of numbers into a quick chart.
Code Editor to edit and preview a snippet without leaving the browser.

Decision tree: pick the developer tool by clipboard - JSON payload opens the JSON Parser; CSS or JS bundle opens the Minifier. — Pick the next click by what is already on your clipboard - a JSON payload opens the JSON Parser, a CSS or JS file opens the matching Minifier.

Tips for reliable results

Keep the original readable source on disk when minifying - you will need it for stack traces. MD5 hashing is for checksums and duplicate detection, not password storage; use a stronger algorithm like SHA-256, bcrypt, or Argon2 for anything credential-related. For diff checks, compare the smallest possible snippets to isolate changes. The tools run in the browser; strip sensitive keys and tokens before pasting if the input is confidential.

Quick comparison

Tool	Best for	Input	Output
JSON Parser	Validate + inspect	JSON text	Tree view + formatted JSON
JS Minifier	Smaller bundles	JavaScript	Minified JS
CSS Minifier	Faster CSS delivery	CSS	Minified CSS
Text Diff	Compare revisions	Two texts	Line-by-line differences
MD5 Converter	Checksums	Text string	MD5 hash

Use cases you can copy

API debugging: Paste a JSON response, validate it, and spot the field that breaks parsing before you deploy.

Release checks: Diff two config files or build outputs to confirm only the intended lines changed.

Minify vs beautify vs obfuscate

Three transformations are often confused. They produce different output and serve different goals.

Minify. Removes whitespace, line breaks, and comments, and shortens local variable names. The runtime behavior is unchanged, and a minified file is trivially reversible with a beautifier. Goal: smaller over-the-wire payload.
Beautify (format). Adds whitespace and indentation back for readability. Functionally identical to the input. Goal: reading a minified or single-line file without changing it.
Obfuscate. Renames identifiers, restructures control flow, and sometimes encodes strings so the result is difficult to read even after beautifying. It is not a security boundary - determined attackers can still reverse it. Goal: raise the cost of casual reverse engineering.

Which to pick. Shipping to production? Minify. Debugging a stack trace? Beautify the minified bundle. Distributing a widget you would rather users did not read? Obfuscate, but pair it with a proper license and server-side checks for anything that actually has to be secret.

Context for common tasks

MD5 is reliable for cache keys, ETags, and file-integrity checksums but not for password storage - a single GPU can hash hundreds of millions of candidates per second, making MD5 passwords trivially brute-forced. Use bcrypt or Argon2id when a human secret is involved.

For data serialization, CSV is the right call when every row has the same flat shape and the downstream tool expects tabular input. JSON handles nested structures and mixed types - and is the format most REST APIs send. The JSON parser lets you validate and reformat in one step before writing a single line of code against it.

Unix timestamps count seconds since 1970-01-01 00:00:00 UTC. The most common off-by-one trap is confusing seconds with milliseconds - the JavaScript Date.now() value is 1,000 times larger than the Unix timestamp for the same moment. The current millis tool shows both values side by side.

Last reviewed: 2026-06-29

Free Tool Online Editorial Team

Last updated: Jul 3, 2026

Reviewed by the Free Tool Online editorial team · Tested in the current versions of Chrome, Firefox, Safari, and Edge before publishing. No account is needed to use any tool. Report a bug - we triage within 72 hours. · Last refreshed April 2026.

Why trust these tools

Ten-plus years of web tooling. The freetoolonline editorial team has shipped browser-based utilities since 2015. The goal has never changed: get you to a working output fast, without an install.
No install, no sign-up. Open a tool and get a working output in seconds - nothing to download and no account to create. Tools that need heavy processing run it on our service, so even a low-powered machine gets the job done.
Analytics stops at the page view. We measure which pages get visited, not what you type or upload inside a tool. There is nothing to sign in to and no profile is attached to your input.
Open-source core components. The processing engines underneath (libheif, libde265, pdf-lib, terser, clean-css, ffmpeg.wasm, and others) are public and audit-able. We link to each one in its tool page's footer.
Free, with or without ads. All tools are fully functional without sign-up. The Disable Ads button in the header is always available if you need a distraction-free run.

Related tools:

MD5 converter - Free online MD5 hash generator and MD5-to-text reverse lookup.
Convert PDF to TEXT online - Extract text from PDF online for copying and editing.
Text To HTML Editor - Text to HTML editor online - write in a WYSIWYG view and watch the generated HTML update live, with
CSS Gradient Animator Generator - CSS gradient generator - build animated linear gradients with live preview; copy ready-to-paste CSS
CSS Minifier - Minify CSS online for faster page loads.
CSS UnMinifier - CSS unminifier online - beautify minified CSS with proper indentation, line breaks, and readable
JavaScript Minifier - JavaScript minifier online free - paste your JS, click Minify, and copy the compressed code.
JSON Parser By Tree View - Paste JSON to validate, format, and view it in a tree.
JavaScript UnMinifier - JavaScript unminifier online - reformat minified JS with indentation and line breaks for
Keyboard Test - Keyboard test online - press each key to highlight it, spot non-working keys, and verify Num Lock,
Text Diff - Text diff online - compare two text blocks and highlight added, removed, and changed characters,
Regex Tester Online - Regex Tester Online - Test a regular expression against your own sample text and watch every match

Tags: #developer

Related guides:

JSON Parser Online: Validate vs Format vs Tree View - Validate, format, or explore JSON?
CSS Minifier vs Compressor - CSS minifier vs compressor - whitespace removal vs gzip/brotli compression, what each saves, and
CSS Unminifier vs Prettier - When to Use Each - When CSS Unminifier is the right tool to read shipped CSS quickly, when Prettier is the right tool
Unix Timestamps Explained - Unix timestamps explained - seconds vs milliseconds, ISO-8601, RFC 2822, UTC vs local time, and the
Milliseconds to Date - UTC vs Local Time - Milliseconds to date conversion: UTC vs local time, why your result may be hours off, and how to
Image to Base64 - Embed in HTML/CSS vs Link the Image File - Should you embed an image as a base64 data URL in HTML/CSS, or link the image file?
QR Code Error Correction and Scan Failures - If a QR code will not scan, the cause is usually one of four: payload size, error-correction level,
MD5 vs SHA-256 - When to Hash - MD5 vs SHA-256 - speed, collision resistance, and concrete use cases.
CSV vs JSON Data Formats - CSV vs JSON data formats - when to pick rows-and-columns vs structured objects, with parsing, size,
Current Time in Milliseconds - Read the current time in milliseconds since the Unix epoch in the browser, copy it for a log line
Time in Milliseconds - A time in milliseconds is a number where 1 second equals 1000 ms.
How to Minify CSS and JS for Cloud Run Cold Start - Minify CSS and JS to cut Cloud Run cold-start and Cloudflare Workers bundle size.

Frequently Asked Questions

When should I minify JavaScript or CSS by hand?

For single-file widgets, email templates, or a one-off embed where you do not have a build step. Paste into JS Minifier or CSS Minifier, ship the minified output to production, and keep the readable source in source control. For real projects, bundle minification into your build (esbuild, Vite, webpack) instead.

Is pasting code into a browser tool safe?

These tools run in the browser, so nothing you paste leaves your device. Even so, strip secrets (API keys, tokens, internal URLs) before pasting, and use a local minifier for code you cannot share with anyone.

My JSON won't validate - what's most likely wrong?

Three common issues: trailing commas after the last key in an object or array, unquoted keys (JSON requires double-quoted keys), and single quotes around strings (JSON only accepts double quotes). Paste into JSON Parser and the error line usually points to the exact character.

What does MD5 Converter help with?

Quick checksums and ID generation for cache keys, file-dedup, or deterministic fingerprints. MD5 is not a password hash - use bcrypt, scrypt, or Argon2 on the server for anything auth-related.

How do I compare two config files without scrolling back and forth?

Use Text Diff. Paste the old version on the left and the new version on the right; the tool highlights line-by-line differences so you can confirm only the intended lines changed before deploying.