This is a collection of small, single-purpose web tools that run entirely inside your browser. There is no account, no upload step and no server-side processing: the JavaScript that does the work is downloaded once with the page, and your files, text and numbers stay on your own device from beginning to end.
That architecture is a deliberate constraint rather than a slogan, and it shapes what these tools can and cannot do. On the good side, there is no queue, no file-size cap imposed by someone else's disk quota, and nothing to leak later — you can compress a folder of client photos, decode a production JWT or work out a salary figure without any of it becoming an entry in a log somewhere. You can also disconnect from the internet after a page loads and keep using it. On the other side, the ceiling is your device: a browser tab has finite memory, and video encoding in particular runs on the CPU rather than dedicated hardware, so a desktop application will still beat the browser on very large jobs. Where that trade-off bites, the relevant category page says so plainly.
The tools are grouped below by what they do. Each category page explains the underlying mechanics — what is lossless and what is not, which standard a tool is measuring against, where an estimate's error bars sit — before listing the tools themselves.