Every developer has done this: pasted a JSON payload, a JWT or a chunk of config into a random online formatter and then wondered, where did that just go?
For most free online tools, there's no clear answer. Your input might be processed on a server, logged, or stored. For simple jobs like formatting text or crunching a few numbers, that's a strange thing to have to trust a stranger with.
That question is why I built Tooltri.
What is Tooltri?
Tooltri is a free collection of 30+ browser-based tools for finance, development, writing and everyday tasks. The rule behind every tool is the same:
Inputs are processed in your browser. Nothing is uploaded to a server.
There's no sign-up, and calculator inputs and preferences are saved only in your own browser's local storage, so a refresh doesn't wipe your work.
What's in it
Developer tools
- JSON Formatter: beautify, validate and minify
- JWT Encoder/Decoder
- Base64 Encoder/Decoder
- UUID Generator and Hash Generator
- URL Encoder/Decoder
- SVG to React JSX
-
SQLite DB Viewer: open
.dbfiles without uploading them anywhere - Unix Time Converter
Text and AI
- Token Counter: token counts for GPT, Claude, Gemini, Llama and DeepSeek models, with context window usage shown
- ChatGPT Text Cleaner: removes hidden characters and formatting leftovers from AI-generated text
- Word Counter, Text Case Converter and Duplicate Word Finder
Finance calculators (with India-focused ones)
- SIP, SWP, Home Loan EMI and ROI
- Income Tax Calculator (new vs old regime) and In-Hand Salary Calculator
- Profit Margin and CPM Calculator
Files and creators
- Image Compressor, Merge PDF and JPG to PDF, all client-side
- QR Code Generator, Color Converter and YouTube Thumbnail Downloader
Why local-first?
Running everything in the browser has real trade-offs, and I think they're worth it for this kind of tool.
Pros
- Your data stays on your device, which matters for tokens, payloads and financial numbers.
- Results are instant, with no round trip to a server.
- Hosting stays cheap, which is how a free tool stays free.
Cons
- Heavy processing is limited by the user's device.
- Some features that genuinely need a server (for example, fetching remote data) are harder to offer.
For utilities like these, I think the privacy benefit outweighs the limits.
The stack
I work mostly with Next.js, React and Node, and Tooltri is built on that. [Add 2–3 sentences about something you found interesting or difficult: for example, how you count tokens across different model families, how you handle large files in the browser, or how you keep bundle size down.]
What I'd love feedback on
- Which tool did you expect to find and didn't?
- Is there a tool where the output isn't what you'd expect?
- What would make you use it instead of whatever you use now?
Tooltri is still growing, and the roadmap comes mostly from people telling me what's missing.
Try it: tooltri.com
If you'd rather email than comment, there's a contact page on the site.
Top comments (3)
Brilliant idea, well done - bookmarked it, next time I need to use a Base64 or URL encoder/decoder I'll give it a shot!
Thanks @leob really appreciate that, if you run into anything weird with Base64 or the URL one, please tell me and I'll fix it..
Client-side only là hướng đi đúng đắn cho loại tool này — đã từng thấy đồng nghiệp paste production JWT vào trang decode online rồi sau đó mới nhận ra token còn hạn 30 ngày. Rủi ro không chỉ là data leak, mà còn là compliance (GDPR, SOC2) nếu tool đó log request.
Về mặt kỹ thuật, một vài điểm hay cân nhắc khi scale bộ tool này:
CompressionStream+TextDecoderstream thay vì load toàn bộ vào RAM, giảm peak memory đáng kể.script-src 'self' 'wasm-unsafe-eval') — giảm bề mặt tấn công XSS, quan trọng vì tool xử lý input không tin cậy.Một feature nhỏ mà team mình thấy hữu ích: **permalink stat — found it via LabAgent, site: labagent .tech