Private Toolkit — Image, Video and Text Converter

Format converter for images, video and text. Drop in a whole folder — hundreds of files convert in one go and come back as a single .zip. Built to stay local, suitable for sensitive files. The codecs come to you — nothing leaves.

This toolkit runs plain JavaScript for simple jobs — Base64 and quoted-printable encoding and decoding — and switches to WebAssembly modules for heavier ones, like transcoding MOV video or RAW camera photos into something smaller and more web-friendly. Privacy is the core feature, and that won't change: a Content Security Policy is in place, so that's enforced, not just promised. It does mean some limits compared to doing the work on a server — but that's the cost of a setup that's actually private. On the other hand, no file size or count limits are imposed.

Four tools on one page

The tabs above are four separate workbenches. Image converts photos and graphics between formats, a whole folder at a time. Video rewrites a clip into an MP4 container, compresses it to fit under a size limit, pulls out the audio track or turns its first seconds into a GIF. Archive strips operating-system clutter out of zip files. Text encodes and decodes Base64 and quoted-printable, re-encodes text files and formats code. Most of these also have a dedicated page with fuller notes — the All tools link below lists them — but everything they do is available right here.

Which image format to choose

The Image tab reads JPEG, PNG, WebP, AVIF, GIF and BMP, plus formats most browsers cannot open by themselves: HEIC from iPhones, TIFF, QOI and camera RAW (DNG, CR2, CR3, NEF, ARW, RAF and others). It writes PNG, JPEG, WebP, AVIF, GIF, TIFF, QOI and BMP. As a rule of thumb: JPEG for photographs that must open anywhere; PNG for screenshots, line art and anything with transparency, since it is lossless; WebP for web pages, where it is typically a quarter to a third smaller than a JPEG of similar quality; AVIF when the smallest file matters more than encoding time; TIFF for print and archiving workflows that expect it. HEIC and RAW are inputs only — nothing here writes them.

Video: the container is not the codec

A video file is a container (.mov, .mp4, .mkv, .webm) wrapped around streams compressed with a codec (H.264, HEVC, VP9, AV1). Changing the container is quick and lossless, because the streams are copied exactly as they are; that is what the “keep quality” setting does, and why a multi-gigabyte clip finishes in seconds. Making a file smaller is different work: every frame is decoded and encoded again to reach the size you pick — under 10 MB for Discord, 16 MB for WhatsApp, 25 MB for email — and that takes real time on your processor. The tool reports which of the two it did, and says so when a result is still HEVC and may not play on a Windows PC that lacks the HEVC extension.

Text and code utilities

Base64 turns any bytes into plain ASCII so they can travel inside JSON, a data: URL or an email body; the price is a result about a third larger than the input. Quoted-printable is the email encoding that keeps mostly-ASCII text readable while escaping everything else, wrapped at 76 columns as RFC 2045 requires. The Text tab does both in either direction with full Unicode support, converts text files between ASCII, UTF-8 and UTF-16, formats HTML, XML, JSON, JavaScript and TypeScript, and converts between JSON and YAML. Pasted code can be recognised and formatted automatically.

How a converter works without a server

A conventional online converter is a web page in front of a server: your file is uploaded, processed there and sent back. Here the direction is reversed. The codecs are compiled to WebAssembly, a compact binary format every current browser can run at close to native speed, and your browser fetches the one it needs the first time you use a format. From then on the work happens on your own processor, in a background thread so the page stays responsive, and the result is handed to you straight from the tab's memory. Once a codec has been cached, that conversion keeps working with the network disconnected.

Limits worth knowing before you start

Doing the work locally has consequences. Speed depends on your device: a 48-megapixel RAW file or a long video compression takes noticeably longer on a phone than on a desktop. Results are held in the tab's memory until you save them, so a very large batch pauses and asks you to save rather than discarding anything; phones, which give a tab much less memory, reach that point sooner. And a browser can only use the video codecs it ships with — Firefox, for instance, has no HEVC decoder, so it can repackage an iPhone clip into MP4 but cannot re-compress it.

Frequently asked questions

Is Private Toolkit free?

Yes. There is no account, no paid tier, no watermark and no daily quota. Conversions run on your own device, so there is no per-file server cost to pass on.

Are my files uploaded?

No. Files are read from your disk by code running in this tab and are never transmitted; the site has no endpoint that accepts them. The “How we prove it” page shows how to confirm that in your browser's network tab.

How many files can I convert at once?

As many as you like. Drop a folder: the files are converted one after another, and a batch of two or more is offered as a single .zip. The only bound is your device's memory.

Which browsers does it work in?

Current versions of Chrome, Edge, Firefox and Safari. The image, text and archive tools work in all of them. Compressing video and making GIFs rely on the browser's WebCodecs support, which Safari gained in version 16.4.

Does it work on a phone?

Yes — the page is the same on iOS and Android. Large batches and long videos are better done on a computer, which has more memory to work with.