When a website processes a file in the cloud, a copy of that file travels across the network and sits on a server while it is worked on. Client-side processing is the opposite: the file stays inside your browser, and the code that handles it runs on your own device. The result is that your document never leaves your browser in the first place.
ThothBox builds on this idea. Its PDF tools use the JavaScript and WebAssembly capabilities built into modern browsers to read, combine, split, and convert PDFs locally. You add a file from your device, the browser does the work, and you download the output — with nothing sent to a server along the way.
That means no upload, no account, no server where your document can sit, and nothing for a service to store, log, or reuse.
Modern browsers ship with powerful built-in capabilities. ThothBox’s tools leverage JavaScript and WebAssembly, a compiled technology that lets browser code run heavier tasks with good performance. When you choose a PDF, the file is read into the browser’s memory on your device, and the tool’s code operates on that local copy.
Nothing about the document is transmitted over the network. Other page assets may load normally, but your file data stays local, and when you download the result it is written from your own browser to your device.
With a server tool, you upload a file, it is processed on the provider’s infrastructure, and you download the result. During that process your document exists on hardware you do not control, and the service usually promises to delete it later. Even a stated retention or deletion policy means the file was uploaded and stored, if only briefly.
A client-side tool removes the server from the workflow. Your document is processed on your device, no copy is created elsewhere, and there is no deletion window to rely on — there is simply no upload. This is the core difference between tools where files never leave your browser and tools that only promise to clean up after themselves.
It means the file is handled by code running in your browser on your device, not by a remote server. Your document stays local for the entire task.
No. ThothBox tools process files in the browser, so your document is never uploaded and never stored on a server.
Yes, the client-side tools are free to use with no signup or payment required.
No. No account, login, or email address is needed.
Yes. Mobile browsers that support the required JavaScript and WebAssembly features can run the tools, and files are still processed locally.
Because processing is local, larger files depend on your device’s browser memory rather than a server limit. Very large documents may take longer or reach browser resource limits.