I'm a tool hoarder. I bookmark everything, forget most of it, and rediscover the same tools six months later through a different Hacker News thread.
But some tools actually stick. The ones I keep coming back to share a few traits: they load instantly, they work offline, they don't need an account, and they do one thing well.
Here are 9 free browser-based developer tools I use regularly. All of them run entirely client-side — your data never leaves your browser.
1. SigCraft — Email Signature Generator
What it does: Generates professional HTML email signatures that actually render correctly across Gmail, Outlook, Apple Mail, and Thunderbird.
Why it's good: Email signatures are deceptively hard. What looks fine in Gmail breaks in Outlook because Microsoft still uses Word's rendering engine (yes, in 2026). SigCraft uses battle-tested table-based HTML that handles these quirks.
You fill in your details, pick a layout, customize colors, and copy the HTML. No account needed.
The pain it solves: Spending 45 minutes hand-coding a signature, only to discover Outlook strips your flexbox.
🔗 SigCraft
2. JSONPretty — JSON Formatter & Validator
What it does: Paste messy JSON, get pretty JSON. Also validates, minifies, and lets you navigate the tree structure.
Why it's better than the alternatives: Most JSON formatters are cluttered with ads or require pasting your API responses into someone else's server. JSONPretty runs 100% in your browser. Paste your production database dump without worrying about it being logged.
Pro tip: Paste a JSON string that contains escaped JSON inside it — JSONPretty handles nested stringified JSON gracefully.
3. RegexLab — Regex Tester
What it does: Write regex patterns, test them against sample text in real-time, and see match highlighting with capture groups.
Why I use it over regex101: Nothing against regex101 — it's excellent. But RegexLab loads faster, works offline, and has a cleaner interface if you just need to quickly validate a pattern. It's the "I need this for 30 seconds" regex tool.
Useful for: Form validation patterns, log parsing, sed/awk one-liners you're testing before running on production.
🔗 RegexLab
4. CronMaker — Cron Expression Generator
What it does: Build cron expressions visually with dropdowns instead of trying to remember if day-of-week is 0-indexed or 1-indexed (it's both, depending on the system).
The killer feature: It shows the next 10 execution times for your expression. No more deploying a cron job and wondering "wait, will this run at 9 AM or 9 PM?"
Supports both 5-field (standard) and 6-field (with seconds) formats.
5. GradientLab — CSS Gradient Builder
What it does: Create CSS linear and radial gradients visually, with real-time preview and one-click CSS copy.
Why it matters: Gradients are one of those CSS features where the syntax is simple but getting the result you want requires tweaking. Moving a color stop from 45% to 52% can transform a gradient from "startup landing page" to "90s WordArt." GradientLab lets you drag things around until it looks right.
6. ColorCraft — Color Palette Generator
What it does: Generate harmonious color palettes with support for complementary, analogous, triadic, split-complementary, and monochromatic schemes. Outputs HEX, RGB, and HSL.
When I use it: Every time I start a side project and need "a few colors that don't look terrible together." Which is roughly every two weeks.
Bonus: It checks contrast ratios for accessibility, so you know your text will be readable before you ship it.
7. PixConvert — Image Format Converter
What it does: Convert images between PNG, JPG, WebP, GIF, BMP, and ICO directly in your browser. Batch conversion supported.
Why browser-based matters here: Image conversion tools love to be "free" with a 5MB limit, then charge you for anything useful. PixConvert has no limits because nothing gets uploaded — the conversion happens with Canvas API in your browser.
I use it for: Converting screenshots to WebP before adding them to blog posts (like this one). Also great for generating .ico files for favicons without installing ImageMagick.
8. Faviconify — Favicon Generator
What it does: Upload an image or type an emoji, and get a complete favicon package: ICO, PNG (multiple sizes), SVG, and the HTML markup to paste in your <head>.
The annoying problem it solves: Favicons in 2026 are still a mess. You need favicon.ico for legacy browsers, apple-touch-icon.png at 180×180 for iOS, favicon.svg for modern browsers, and manifest.json icons at 192 and 512 for PWAs. Faviconify generates all of them from one source image.
9. LegalPage — Privacy Policy & Terms Generator
What it does: Generates privacy policies and terms of service for your web app. Fill in your company name, what data you collect, and which third-party services you use. Get a markdown or HTML document.
Real talk: You need a privacy policy. GDPR requires it. The App Store requires it. Even a simple analytics-free static site technically needs one if you're in the EU. But paying a lawyer $500 for a side project making $0/month doesn't make sense.
LegalPage generates reasonable templates that cover the basics. Not legal advice, but infinitely better than having nothing.
Why These Tools Are All Client-Side
Every tool on this list runs entirely in your browser. No server, no database, no account.
This isn't just a privacy benefit — it's a reliability one. These tools will still work when:
- Your internet drops during a flight
- The hosting company has a bad day
- The developer gets bored and stops paying for servers
Static sites on GitHub Pages are effectively immortal. The code is open source. If the developer disappears, fork it and host it yourself.
The Pattern
The best developer tools share a few traits:
- Do one thing well. Not a "platform" — a tool.
- No signup required. If I have to create an account to format JSON, something has gone wrong.
- Works offline. Or at least degrades gracefully.
- Respects privacy. Your data is your data.
- Fast. Sub-second load times. No spinner.
If you're building developer tools, steal this pattern. It works.
Found this useful? I'm building more tools like these. Follow @maboroshi on dev.to or star the repos on GitHub to stay in the loop.
What free dev tools do you use daily that more people should know about? Drop them in the comments — I'm always looking for new ones.
Top comments (0)