Post · Technology
Why VoltKit Runs in Your Browser, Not on a Server
Most online tools upload your files to a server. VoltKit doesn't. What browser-side processing means, why it is faster and more private, and its limits.
- Author
- VoltKit
- Published
- Reading time
- 2 min read
When you drop a photo into a typical online compressor, it travels to a server, gets processed there, sits in storage for a while, and comes back. The site promises to delete it. VoltKit takes a different route: the photo never leaves your computer. This post explains how that works and why we chose it.
What "in the browser" means
Modern browsers ship with powerful built-in capabilities, all available to JavaScript running on a web page:
- The Canvas API can decode, resize and re-encode images.
- The File API reads files you select without uploading them.
- Web Crypto generates random values for things like UUIDs.
- JavaScript libraries can build PDFs, parse JSON and run calculations.
VoltKit's tools use these directly. When you compress an image, your browser decodes it, redraws it at the chosen quality, and hands you the result as a download. The only network traffic is the page itself.
Why it is better for you
Privacy by construction. We cannot leak, sell or lose files we never receive. Contracts, ID documents and medical scans are exactly the files people process most, and they stay on your device.
Speed. There is no upload and no download of the result. A 5 MB photo compresses in the time it would have taken to start uploading it.
Works offline and on slow connections. Once the page has loaded, the tool keeps working without a connection.
No queues, no limits. Server-side tools ration their capacity with file-size caps and daily limits. Your laptop is the only limit here.
Why it is better for us
Running servers that process strangers' files is expensive and risky. Skipping them keeps VoltKit free without aggressive advertising, and it keeps the codebase small: a tool is a pure function from input to output, testable in isolation.
Where the limits are
Browser processing is not free of trade-offs, and we would rather say so:
- Very large files depend on your device's memory. A 200-megapixel image may fail on a phone.
- Some encoders are missing. Older Safari cannot create WebP images, so that option is disabled there rather than faked.
- Heavy jobs such as OCR or background removal need large models. Some of them can run in the browser with WebAssembly; others may be worth a server. If we ever add a server-assisted tool, its page will say so clearly, and the browser-only tools will stay browser-only.
How to check for yourself
Open your browser's developer tools, choose the Network tab, and use the image compressor or the JWT decoder. Watch the requests: scripts and styles load, and then nothing. That silence is the whole point.
Frequently asked questions
How can I verify that nothing is uploaded?
Open your browser's developer tools, switch to the Network tab, and use any tool. You will see the page and its scripts load, but no request carrying your file or text.
Does that mean VoltKit collects nothing at all?
The tools themselves send nothing. We count page views with Cloudflare Web Analytics and Google Analytics, and our hosting provider keeps standard server logs. All three are described in the privacy policy.