Every tool on this site runs as code inside your browser. When you drop a file onto a converter, the browser reads it from your disk into memory, transforms it, and hands the result back as a download. At no point does the file travel over a network.
Why that is possible now
Image and PDF conversion used to require a server because browsers could not run the necessary codecs. That changed with WebAssembly, which lets compiled C and Rust libraries — the same ones a server would use — run at close to native speed inside a web page.
Rasp uses that directly. JPEG, PNG, WebP and AVIF are handled by codecs derived from Google's Squoosh project. HEIC is decoded by libheif, compiled to WebAssembly. PDFs are assembled with pdf-lib, which is plain JavaScript. All of it executes on your machine.
Why the work happens in a Web Worker
Decoding a large photo takes real processing time. Run on the main thread, it would freeze the page — buttons would stop responding and scrolling would stutter. Each converter therefore runs in a Web Worker, a separate thread, so the interface stays responsive while the file is processed.
What the network readout measures
Under every result is a readout labelled Uploaded. It is not a decorative badge. It is connected to this page's own network layer and counts the bytes of every request body the page sends.
It reads zero because the conversion genuinely has no network path — not because zero has been printed there. Advertising and analytics requests are excluded from the count, since they carry none of your file's data and including them would obscure the one number the readout exists to report.
What this means in practice
- No file size limit. Upload caps exist because bandwidth costs money. No bandwidth is used here, so your device's available memory is the only ceiling.
- No queue. You are not sharing a server with anyone, so conversion starts immediately.
- There is no account, ever. Nothing to sign up for and nothing to log in to, because there is no server holding anything an account would protect.
- Your originals are never modified. Files are read, never written back.
The honest limitations
Local processing is not free of trade-offs, and it would be misleading to pretend otherwise:
- Very large batches can exhaust memory, particularly on phones. A desktop browser handles far more at once.
- The first conversion on a page downloads the relevant codec, which for HEIC is a few megabytes. Subsequent conversions are instant.
- Some conversions genuinely need a server's resources and are not offered here rather than being done badly.
How the site is paid for
Rasp carries advertising. That is what funds the hosting and the work of building the tools, and it is why the tools are free and require no account. Ads are kept out of the working area of every tool: a cluttered, untrustworthy interface would undermine the only thing that makes this site worth using.