Free Online Developer Tools I Actually Reach For (No Signup, No Uploads)

The ones I use almost daily

If I had to keep only five tabs, these would be them.

• JSON Viewer & Beautifier — I paste ugly API responses here more than I’d like to admit. The tree view collapses deep objects so I can actually find the one field I care about. It also flags where your JSON is broken instead of just throwing a vague error.
• API Request Tester — for a quick GET or POST I don’t want to open Postman and wait for it to boot. Headers, auth, body, and it’ll spit out a cURL or fetch snippet. One honest caveat: browser CORS will block some third-party APIs (there’s a proxy toggle for that). I wrote a whole piece on testing an API in the browser.
• Regex Tester — live highlighting and capture groups. I still get regex wrong constantly; this just shortens the loop between “wrong” and “less wrong.”
• JS to JSON Converter — for when someone pastes a JavaScript object with unquoted keys and trailing commas and expects it to be valid JSON. It isn’t. This fixes it.

Image stuff, without the upload anxiety

The thing I genuinely care about with image tools: my screenshots often have client data, tokens, or someone’s email in them. These run locally, so nothing leaves the laptop.

• Image Annotator — arrows, boxes, numbered steps, and a redaction tool that blurs or blacks out the bits you don’t want shared. If you send a lot of bug reports, see how to redact a screenshot properly.
• Image Compressor and Image Resizer — the boring duo I use before uploading anything to a site I’m building. You control the quality, so you’re not at the mercy of some default.
• Image Crop and Color Palette Extractor — cropping to an exact ratio, and pulling hex codes out of a screenshot when a designer hands me a PNG instead of a style guide.

The “I only need this once a month” pile

Not daily, but when I need them I really need them, and I never remember the syntax.

• Cron Expression Generator — because I will never memorise what 0 */6 * * * means, and I’m done pretending I will.
• QR Code Generator — static codes that don’t expire and don’t route through someone’s tracking redirect. Important if you’re printing them.
• Password Generator, Base64 Image Converter, Favicon Generator — the utilities that each save me a five-minute detour.
• Markdown to HTML, Text Analyzer, Color & Gradient Converter — for writing, content checks, and stealing… I mean, generating CSS gradients.

Why “runs in the browser” matters more than it sounds

Half the “free” online tools out there quietly upload your file to a server to do the work. For a meme, fine. For a screenshot of your production dashboard or a JSON blob with a live API key in it, that’s a leak waiting to happen. Tools that process everything client-side don’t have that problem — the data physically never leaves your machine. That’s the whole reason I built most of the ones above.

The honest trade-off: client-side tools can choke on genuinely huge files (a 200MB image, a 50MB JSON), because your browser is doing the lifting. For day-to-day work it’s a non-issue, but it’s worth knowing before you throw something enormous at one.

Frequently asked questions

Are these actually free, or “free until you hit a wall”?

Actually free. No account, no credit card, no “upgrade to export.” They’re web tools, not a trial.

Do I need to install anything?

No. Open the page and use it. That’s the entire point.

Is my data safe?

For the tools above, the work happens in your browser and nothing is uploaded. Your files and text stay on your device.