25 Best Free Developer Tools for Everyday Coding in 2026

Every developer has their collection of bookmarked tools. The json formatter you've used for years. The diff checker that's saved you hours. The random image converter you found that actually works.

Here's a rundown of the tools that belong in every developer's toolkit, organized by what you're trying to do.

Data Formatting & Validation

JSON Formatter You'll use this weekly if not daily. Paste in minified JSON, get readable output with proper indentation. Good ones also validate and point out syntax errors.

csv to json Converter For when you get spreadsheet data that needs to go into an API. Also works the other way when you need to export JSON to Excel.

base64 encoder/Decoder Essential for data URIs, API tokens, and debugging encoded strings. Used more often than you'd expect.

url encoder/Decoder Debugging query strings, handling special characters in URLs. Small but necessary.

Text & Code Tools

Diff Checker Compare two versions of code or text. Crucial for code reviews, debugging, and understanding what changed between versions.

Word Counter Quick way to check article length, character limits, reading time. Also handles case conversion and whitespace cleanup.

Markdown Preview Write Markdown and see it rendered in real-time. Especially useful for README files and documentation.

HTML/CSS/JS Editor Online code playground for quick experiments. Test snippets without firing up your whole dev environment.

Image Tools

Image Compressor Reduce file sizes for web use without visible quality loss. Every website needs optimized images.

Image Resizer Change dimensions while maintaining aspect ratio. Bulk social media prep, thumbnail creation.

image to pdf Combine multiple images into a single PDF. Useful for documentation, invoices, portfolios.

image to base64 Convert images to data URIs for embedding directly in HTML or CSS. No external file needed.

Developer Utilities

Timestamp Converter Convert Unix timestamps to human-readable dates and back. APIs use timestamps everywhere.

Slug Generator Create URL-friendly slugs from titles. Essential for CMS work and SEO.

regex generator Get AI help writing regular expressions from plain English descriptions. Regex is hard; help is good.

meta tag generator Create proper seo meta tags, open graph tags, and twitter cards. Copy-paste into your HTML.

Responsive Design Checker Preview how sites look across different screen sizes. Mobile, tablet, desktop views without resizing your browser.

The Privacy Factor

Here's something that matters: where does your data go?

Many online tools send your code, text, or images to their servers. That might be fine for random test data, but not for:

• Production API responses with user data
• Internal company documents
• Source code that shouldn't leave your machine

Look for tools that run entirely in the browser. Your data stays on your computer.

Why Bookmarking Matters

The best tools are the ones you can find when you need them. Having a reliable set of bookmarked tools means:

• No searching every time you need to format JSON
• Consistent experience (you know how the interface works)
• No time wasted evaluating new tools repeatedly

Build your collection once, use it forever.

Our Toolset

Everything on FormatMint was built with this philosophy:

• Runs in your browser. No server uploads for most tools.
• No signup. Just use the tool.
• No ads or dark patterns. Clean interface, focused functionality.
• Free. Because basic developer utilities shouldn't cost money.

Check out the full list of tools and bookmark the ones you'll use. Your future self debugging at 2 AM will thank you.