10 Free Browser Tools Every Developer Should Bookmark (No Signup, No Ads)

I keep bookmarking web tools and then forgetting where I saved them. So I started collecting the ones I actually use into a single page. Here are 10 that I reach for constantly — all free, all run in-browser, no signup needed. Developer Tools 1. JSON Formatter & Validator Paste JSON, get it pretty-printed with syntax highlighting. More importantly: it tells you exactly where the error is, with line and column numbers. Better than most VS Code extensions for quick validation. 2. Base64 Encoder/Decoder Text, files, and JWTs. The JWT decode mode saves me from going to jwt.io every time I need to inspect a token. Drag-and-drop file encoding is a nice touch. 3. AI Token Counter Paste a prompt, see estimated token counts for GPT-4o, Claude, and Llama. Shows cost estimates too. Essential if you're building anything with LLM APIs and trying to stay under budget. 4. Link Preview Checker See how your Open Graph tags will render on Google, Twitter, Discord, WhatsApp, LinkedIn, Slack, and iMessage