Almost all of Wizard Toolbox's code was written for Wizard Toolbox. The exceptions, in full:
LAME (MP3 encoding)
MP3 files are encoded by LAME, via the lamejs JavaScript port (the @breezystack/lamejs fork, version 1.2.7, shipped verbatim at /js/vendor/lamejs.js). LAME is the open-source MP3 encoder from lame.sourceforge.io; the port lives at github.com/zhuker/lamejs. It is licensed under the GNU Lesser General Public License - the full text, with LAME's own usage notes, is at LICENSE-lamejs.txt. Like everything else here it runs entirely in your browser; your audio is encoded on your own machine.
PDF.js and pdf-lib (PDF tools)
The PDF tools read and draw PDFs with PDF.js, Mozilla's PDF renderer (pdfjs-dist 6.3.289, shipped verbatim under /js/vendor/pdfjs/), licensed under the Apache License 2.0: PDF.js license. It brings the Foxit and Liberation fonts it substitutes for fonts a PDF does not embed (Foxit license · Liberation license) and image decoders built from OpenJPEG, PDFium's JBIG2 decoder and qcms (OpenJPEG · JBIG2 · qcms). PDFs are written with pdf-lib by Andrew Dillon (version 1.17.1, shipped verbatim at /js/vendor/pdf-lib.esm.min.js), under the MIT License: pdf-lib license. Both run in your browser; your PDFs are never uploaded.
js-beautify, sql-formatter and Terser (Code Formatter)
The Code Formatter lays out HTML, CSS and JavaScript with js-beautify by Einar Lielmanis, Liam Newman and contributors (version 1.15.4, shipped verbatim at /js/vendor/js-beautify.min.js, MIT License: js-beautify license) and SQL with sql-formatter (version 15.8.2, shipped verbatim at /js/vendor/sql-formatter.min.js, MIT License: sql-formatter license). It minifies JavaScript with Terser by Mihai Bazon and contributors (version 5.51.2, its browser bundle minified by Terser itself and shipped at /js/vendor/terser.min.js, BSD 2-Clause License: Terser license). All three are loaded only when the tool needs them and run in your browser.
SVGO (SVG Optimizer)
The SVG Optimizer runs SVGO, by Kir Belevich and its contributors (version 4.1.0, its browser build shipped verbatim at /js/vendor/svgo.browser.js), under the MIT License: SVGO license. It runs in your browser; your SVG files are never uploaded.
Typefaces
Headlines are set in Bricolage Grotesque (by Mathieu Triay), body text in Inter (by Rasmus Andersson) and format labels in JetBrains Mono (by JetBrains). All three are licensed under the SIL Open Font License 1.1 and served from this site rather than from a font network: Bricolage Grotesque license · Inter license · JetBrains Mono license.
Everything else
The converters, the other tools, the detection, the pages and the build are original to this project, and the site makes no requests to any third party.