About BoltConverter
File conversion that is genuinely free, genuinely private, and fast enough to feel instant. No tricks, no upsells, no account required — ever.
Why we built it
Every existing file converter falls into one of two traps: either it makes you sign up for a free trial that eventually turns into a paid subscription, or it quietly uploads your photos and documents to a server you know nothing about. We built BoltConverter to offer a genuine alternative — something honest about what it does and why it is free.
The name comes from our core design principle: conversion should be as fast as a lightning bolt. Most format conversions are deterministic math — they do not require a cloud server at all. WebAssembly lets modern browsers run near-native code, so HEIC decoding, PNG compression, and audio transcoding can all happen directly in your browser tab, on your device, with no network round-trip.
How privacy actually works here
Images and audio — in your browser only
Formats like HEIC, PNG, WebP, MP3, and WAV are converted using WebAssembly libraries that run entirely inside your browser tab. Your file is read from your disk, processed in memory, and the result is written back to your disk. At no point does any byte of your file travel over a network connection.
Documents — processed and deleted
PDF, Word, Excel, and similar formats require native rendering engines that are too large to ship as WebAssembly. These conversions go to our server, run in an isolated container, and the resulting file is streamed directly to your browser. We do not write your document to disk and we do not keep logs of file content. The in-memory process terminates as soon as the download is complete.
What "actually free" means
BoltConverter is free because we show non-intrusive ads on converter pages. There is no freemium tier with hidden limits, no watermarking, and no cap on how many files you can convert. If a converter is on this site, it is free to use as many times as you want.
We do not sell user data, build advertising profiles, or share information with third parties beyond what is disclosed in our privacy policy.
The technical bit
Client-side conversions use mature, audited WebAssembly ports of well-known libraries: libheif for HEIC, canvas APIs for general image operations, and FFmpeg-derived libraries for audio. The browser runs these at near-native speed — a typical iPhone HEIC photo converts in under two seconds on a mid-range laptop.
Server-side conversions run on Cloudflare's global edge network. The code that handles your file is isolated per-request inside a Worker container. There is no persistent storage, no database of uploaded files, and no logging of file contents.
The site itself is built with Astro, deployed as a Cloudflare Worker. Pages are server-rendered at the edge for fast first loads and full SEO indexability, with client-side JavaScript only where conversion logic requires it.