About OnDevice Tools

Why this site exists

Most free online tools work the same way: you choose a file, the page uploads it to a server you know nothing about, something happens there, and a result comes back. For a throwaway snippet that is fine. For a contract, a passport scan, a database dump or a JSON Web Token from a live environment, it is a decision most people would not make consciously if the page said out loud what it was doing.

OnDevice Tools was built to remove that decision. Every tool here is written in JavaScript that runs on your own machine. Your file is read by the browser, processed by the browser, and handed back by the browser. There is no upload step to opt out of, because there is no server capable of receiving one.

How it actually works

The site is a static build. Each of the 63 tools is prerendered to plain HTML at build time and served as a file from a CDN — the same way an image is served. When you open a tool, the browser downloads a small JavaScript bundle for that one tool and runs it locally.

The heavy lifting uses capabilities browsers already ship: the Canvas API for image compression and resizing, the File API for reading files you choose, Web Crypto for hashing, and the built-in JSON and text parsers for the developer tools. Longer jobs run in a Web Worker so the page stays responsive. Nothing about that pipeline involves a network request.

A service worker caches the app after your first visit, so the tools keep working with no connection at all. That is the simplest proof of the claim: something that genuinely uploads your data cannot run on a plane.

What this means in practice

• It is instant. No upload, no queue, no round trip.
• It works on files you should not upload. Client data, credentials, anything under an NDA.
• There is no size limit imposed by a server — only what your own device can comfortably hold in memory.
• It works offline once cached, including on a plane or a train.
• There is no account. Nothing to sign up for, nothing to cancel.

Who builds it

OnDevice Tools is built and maintained by Priyabrata Saha, an independent developer. It started in 2026 as a handful of tools that solved problems I kept hitting, and grew as I got tired of pasting things into sites I did not trust.

It is a one-person project, which is why tools ship steadily rather than all at once, and why the feedback loop is short: if something is wrong, mail support@ondevice-tools.org and it usually gets fixed the same week.

How it is paid for

Serving static files from a CDN costs very little, which is the main reason this can be free with no usage limits. Running costs are covered by advertising. Ads are display units on the page — they never see the contents of the tool you are using, because that content is never sent anywhere for them to see.

Exactly what advertising does and does not have access to is set out on the privacy page, in plain language.

If you would rather support the site directly than see ads, you can buy me a coffee. It is genuinely optional: there is no membership, no ad-free tier and nothing withheld from anyone who does not.

What is not here

No account system, no cloud storage, no sync between devices, no team features and no paid tier. Those would all require a backend, and the absence of a backend is the entire point. If you need a tool that remembers your work across machines, this is the wrong site — and that is a deliberate trade.

Get in touch

Bug reports and tool requests go to support@ondevice-tools.org, anything else to contact@ondevice-tools.org — see the contact page for which is which. Requests for a tool that would need a server get an honest no rather than a maybe.