When you use an online tool to compress a photo, convert a file, or generate a password, where does your data actually go? For many websites, the answer is: to their servers. But a growing number of tools — including all of ours — do the work entirely inside your browser, so your files never leave your device. Here's what that means and why it matters.

Two ways an online tool can work

Broadly, an online tool processes your data in one of two places:

• On a server (uploaded): your file is sent over the internet to the company's computers, processed there, and sent back. The company — and anyone with access to that server — could in principle see, copy, or keep your file.
• In your browser (local): the tool runs as code inside the web page you've opened, using your own device's processor. Your file is read and transformed right there on your screen. Nothing is uploaded.

Modern browsers are powerful enough to do a huge amount locally — resizing images, reading text from files, running calculations, even lightweight machine learning — all without a round trip to a server.

Why local processing is more private

If a file never leaves your device, there's simply nothing to intercept, leak, or misuse. This matters more than people realise, because the things we run through online tools are often sensitive:

• Photos that may contain faces, documents, or location data
• PDFs and spreadsheets with personal or financial details
• Passwords and other credentials
• Draft writing you'd rather not have logged somewhere

With a browser-based tool, you don't have to trust a company's data-retention policy, because there's no upload in the first place. That's the reasoning behind our password generator, which creates passwords using your browser's built-in secure randomness and never transmits them anywhere.

It's usually faster, too

Uploading a large file and waiting for a server to process and return it takes time — and if your connection is slow, a lot of it. Local tools skip that entirely. When you drop a photo into our image compressor, it processes instantly because there's no upload and no queue. The bigger your file, the more obvious the speed difference becomes.

How to tell which kind you're using

A few clues suggest a tool runs locally:

• It works even after you go offline (try switching off your Wi‑Fi once the page has loaded).
• Large files process instantly, with no "uploading…" progress bar.
• The site explicitly says your files "never leave your device" or are "processed in your browser".

If a tool shows a long upload bar for a small file, it's probably sending your data to a server. That's not always a problem — but it's worth knowing.

The bottom line

Browser-based tools give you the best of both worlds: the convenience of a website with the privacy of software that runs on your own machine. It's why every tool in the Playful Souls toolkit is built to run locally. Your files are yours — they should stay that way.