Altto’s tools run in your browser. Most of the code is Altto’s own; some comes from free, open-source projects, and every font is open-licence. They are all served from altto.co.uk itself (nothing is loaded from other sites), copied unchanged from their official packages, each with its licence file alongside it in /lib/. This page lists them with their licences. Thank you to everyone who makes them.
Altto’s own code includes the Publisher (.pub) file reader, the Windows metafile (WMF/EMF) reader and the Altto Layout editor, which were written for altto.co.uk and don’t contain code from other projects. © 2026 altto.co.uk.
Code libraries
| Library | Licence | By |
|---|---|---|
| @huggingface/transformers 4.3.0 | Apache-2.0 | Hugging Face |
| onnxruntime-web 1.31.0-dev.20260914-8d85527a0 | MIT | Microsoft |
| onnxruntime-web 1.30.0 | MIT | Microsoft |
| pdf-lib 1.17.1 | MIT | Andrew Dillon |
| pdfjs-dist 3.11.174 | Apache-2.0 | Mozilla |
| tesseract.js 5.1.1 | Apache-2.0 | Project Naptha |
| xlsx 0.20.3 | Apache-2.0 | SheetJS |
| jspdf 2.5.1 | MIT | James Hall and contributors |
| heic-to 1.5.2 (includes libheif 1.22.2) | LGPL-3.0 | Hopper Gee; libheif by struktur AG |
| heic2any 0.0.4 | MIT | Alex Corvi |
| html2canvas 1.4.1 | MIT | Niklas von Hertzen |
| pptxgenjs 3.12.0 | MIT | Brent Ely |
| @contentauth/c2pa-web 0.15.1 | MIT | Adobe / Content Authenticity Initiative |
| rtf.js 3.0.9 | MIT | Thomas Bluemel |
| @jsquash/jxl 1.3.0 | Apache-2.0; libjxl BSD-3-Clause | Jamie Sinclair / Google (Squoosh) |
| @neslinesli93/qpdf-wasm 0.3.0 | ISC (qpdf itself: Apache-2.0) | neslinesli93 / Jay Berkenbilt |
| cfb 1.2.2 | Apache-2.0 | SheetJS |
| mammoth 1.8.0 | BSD-2-Clause | Michael Williamson |
| Tesseract trained data (tessdata_best) | Apache-2.0 | |
| @pdf-lib/fontkit 1.1.1 | MIT | Andrew Dillon (pdf-lib fork of fontkit by Devon Govett) |
Fonts
Fonts used by the editors (Edit PDF, Sign PDF and Altto Layout) and by the site itself. Some are made to the same measurements as common Microsoft Office fonts, so documents keep their layout; they are separate designs, not copies of those fonts.
| Font | Licence | Package |
|---|---|---|
| Anton | SIL Open Font License 1.1 | @fontsource/anton 5.3.0 |
| Archivo Narrow | SIL Open Font License 1.1 | @fontsource/archivo-narrow 5.3.0 |
| Arimo | Apache-2.0 | @fontsource/arimo 5.3.0 |
| Bebas Neue | SIL Open Font License 1.1 | @fontsource/bebas-neue 5.3.0 |
| Cabin | SIL Open Font License 1.1 | @fontsource/cabin 5.3.0 |
| Caladea | Apache-2.0 | @fontsource/caladea 5.3.0 |
| Carlito | SIL Open Font License 1.1 | @fontsource/carlito 5.3.0 |
| Caveat | SIL Open Font License 1.1 | @fontsource-variable/caveat 5.3.0 |
| Comic Neue | SIL Open Font License 1.1 | @fontsource/comic-neue 5.3.0 |
| Cousine | Apache-2.0 | @fontsource/cousine 5.3.0 |
| Dancing Script | SIL Open Font License 1.1 | @fontsource-variable/dancing-script 5.3.0 |
| EB Garamond | SIL Open Font License 1.1 | @fontsource/eb-garamond 5.3.0 |
| Gelasio | SIL Open Font License 1.1 | @fontsource/gelasio 5.3.0 |
| Homemade Apple | SIL Open Font License 1.1 | @fontsource/homemade-apple 5.3.0 |
| Inter | SIL Open Font License 1.1 | @fontsource-variable/inter 5.3.0 |
| JetBrains Mono | SIL Open Font License 1.1 | @fontsource-variable/jetbrains-mono 5.3.0 |
| Lato | SIL Open Font License 1.1 | @fontsource/lato 5.3.0 |
| Libre Baskerville | SIL Open Font License 1.1 | @fontsource/libre-baskerville 5.3.0 |
| Libre Franklin | SIL Open Font License 1.1 | @fontsource/libre-franklin 5.3.0 |
| Lobster | SIL Open Font License 1.1 | @fontsource/lobster 5.3.0 |
| Lora | SIL Open Font License 1.1 | @fontsource/lora 5.3.0 |
| Merriweather | SIL Open Font License 1.1 | @fontsource/merriweather 5.3.0 |
| Montserrat | SIL Open Font License 1.1 | @fontsource/montserrat 5.3.0 |
| Noto Sans | SIL Open Font License 1.1 | @fontsource/noto-sans 5.3.0 |
| Open Sans | SIL Open Font License 1.1 | @fontsource/open-sans 5.3.0 |
| Oswald | SIL Open Font License 1.1 | @fontsource/oswald 5.3.0 |
| Pacifico | SIL Open Font License 1.1 | @fontsource/pacifico 5.3.0 |
| Playfair Display | SIL Open Font License 1.1 | @fontsource/playfair-display 5.3.0 |
| Poppins | SIL Open Font License 1.1 | @fontsource/poppins 5.3.0 |
| Questrial | SIL Open Font License 1.1 | @fontsource/questrial 5.3.0 |
| Raleway | SIL Open Font License 1.1 | @fontsource/raleway 5.3.0 |
| Roboto Condensed | SIL Open Font License 1.1 | @fontsource/roboto-condensed 5.3.0 |
| Roboto Slab | Apache-2.0 | @fontsource/roboto-slab 5.3.0 |
| Space Grotesk | SIL Open Font License 1.1 | @fontsource-variable/space-grotesk 5.3.0 |
| Tinos | Apache-2.0 | @fontsource/tinos 5.3.0 |
Trademarks
Microsoft, Publisher, Word, Excel and PowerPoint are trademarks of Microsoft Corporation. Adobe and Acrobat are trademarks of Adobe. Altto is not affiliated with or endorsed by Microsoft or Adobe; their names are used only to say which files Altto works with.
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