Third-party licences
Every conversion on ConverterStack happens locally — your files stay in your browser and are never uploaded anywhere. That also means the open-source libraries below are downloaded to your device and run there. They are listed here with their versions, licences and sources, so you can see exactly what runs on your machine. For a plain-language explanation of how each converter works, see How it works on the About page.
Image decoding
heic-to 1.5.2 — LGPL-3.0-or-later
Decoding Apple HEIC/HEIF photos in the browser.
libheif (bundled by heic-to) 1.22.2 — LGPL-3.0
HEIF container parsing and image decoding.
libde265 (bundled by heic-to) — LGPL-3.0
HEVC decoding, the compression used inside HEIC photos.
heic-to, together with the libheif and libde265 builds it bundles, is used unmodified. It is loaded as its own separately addressable JavaScript chunk, downloaded only when you convert a HEIC file. You may therefore substitute your own build of the library — for example by serving a modified chunk in its place — and the rest of the site will keep working. This is how ConverterStack meets the relinking requirement in section 4(d) of the LGPL-3.0.
Audio and video
mediabunny 1.58.0 — MPL-2.0
Audio and video conversion via the browser's WebCodecs API.
@mediabunny/mp3-encoder 1.58.0 — MPL-2.0
Encoding MP3 audio, which no browser can do on its own. Built from LAME, compiled to WebAssembly.
LAME (bundled by @mediabunny/mp3-encoder) — LGPL-2.1-or-later
The MP3 encoding algorithm itself.
mediabunny is used unmodified. The complete source code for the version shipped here can be obtained from the mediabunny repository on GitHub or from the mediabunny 1.58.0 package on npm, as required by section 3.2 of the MPL-2.0.
The MP3 encoder is a separate extension package, also MPL-2.0 and also used unmodified. It contains a WebAssembly build of LAME, which is licensed under the LGPL-2.1. Like the HEIC decoder it is downloaded as its own chunk, only when you convert to MP3, so you can substitute your own build of it.
Documents
pdfjs-dist 6.3.289 — Apache-2.0
Rendering PDF pages so they can be saved as images.
@cantoo/pdf-lib 2.11.1 — MIT
Creating PDF documents from images.
tslib 2.8.1 — 0BSD
TypeScript runtime helpers, a dependency of @cantoo/pdf-lib.
culori 4.0.2 — MIT
Colour conversion, a dependency of @cantoo/pdf-lib.
fflate 0.8.3 — MIT
Deflate compression of PDF streams, a dependency of @cantoo/pdf-lib.
node-html-better-parser 1.5.9 — MIT
HTML parsing, a dependency of @cantoo/pdf-lib.
Framework
next 16.3.3 — MIT
The framework this site is built and statically exported with.
react and react-dom 19.2.8 — MIT
The user-interface runtime.
The MIT, 0BSD and Apache-2.0 libraries are used under their respective licences, with their copyright and permission notices retained in the files served to your browser. If an attribution here is missing or wrong, please let us know.
ConverterStack itself is open source under the MIT licence. View or contribute to the source on GitHub.