Licenses and credits
solopdfs relies on free and open source software created by others. This page lists each third-party component downloaded by your browser when using the site, with its license, and serves the full license texts from this same website.
For each component, we state what we know and how we know it. Where the exact list is not yet confirmed, we state it plainly: “list pending confirmation”. We do not publish unverified details.
PDF engine: PDFium in WebAssembly
Merge, split, rotate, compress, sign, JPG to PDF, and PDF to JPG use PDFium, compiled to WebAssembly (a single file downloaded with the page). Several third-party libraries are linked inside that file.
FreeType notice
FreeType is used under the FreeType Project License, which requires this notice. The years are those stated by the license text we publish at /licenses/freetype.txt; the PDF engine does not say which exact FreeType version it contains, so we cannot give the year of that version.
Portions of this software are copyright © 1996-2002, 2006 The FreeType Project (www.freetype.org). All rights reserved.
The license texts for these libraries come from the PDFium build used by Solo2 in its native applications. They are indicative until the exact PDFium revision and bundled libraries in this site's WebAssembly file are confirmed.
PDFium
Reads and writes PDF. The distributing package does not indicate the contained PDFium revision.
- Version
- to be confirmed
- License
- BSD-3-Clause, Apache-2.0
- Copyright
- Copyright 2014 PDFium Authors. All rights reserved.
- Status
- confirmed by the package that distributes it
- Full text
- pdfium.txt
@embedpdf/pdfium
JavaScript code bridging the page with PDFium, unmodified.
- Version
- 2.15.1
- License
- MIT
- Copyright
- Copyright (c) 2024 CloudPDF, Ji Chang
- Status
- confirmed by the package that distributes it
- Full text
- embedpdf-pdfium-wrapper-MIT.txt
libpng
PNG images within PDFs. The version can be read directly in the WebAssembly file.
- Version
- 1.6.43
- License
- PNG Reference Library License version 2
- Copyright
- Copyright (c) 1995-2026 The PNG Reference Library Authors; Cosmin Truta; Glenn Randers-Pehrson; Andreas Dilger; Guy Eric Schalnat, Group 42, Inc.
- Status
- detected inside the WebAssembly file
- Full text
- libpng.txt
FreeType
Font rendering.
- Version
- to be confirmed
- License
- FreeType Project License (FTL)
- Copyright
- Copyright 1996-2002, 2006 by David Turner, Robert Wilhelm, and Werner Lemberg
- Status
- detected inside the WebAssembly file
- Full text
- freetype.txt
OpenJPEG
JPEG 2000 images within PDFs.
- Version
- to be confirmed
- License
- BSD-2-Clause
- Copyright
- Copyright (c) 2005, Herve Drolon, FreeImage Team; (c) 2008, 2011-2012, Centre National d'Etudes Spatiales (CNES), FR; (c) 2012, CS Systemes d'Information, France
- Status
- detected inside the WebAssembly file
- Full text
- openjpeg.txt
Little CMS (lcms2)
Color management (ICC profiles).
- Version
- to be confirmed
- License
- MIT
- Copyright
- Copyright (c) 1998-2026 Marti Maria Saguer
- Status
- detected inside the WebAssembly file
- Full text
- lcms.txt
zlib
Data compression.
- Version
- to be confirmed
- License
- zlib License
- Copyright
- Copyright (C) 1995-2026 Jean-loup Gailly and Mark Adler
- Status
- detected inside the WebAssembly file
- Full text
- zlib.txt
Other libraries that PDFium may include
These libraries are typically included within PDFium, but we have not been able to confirm their presence in the WebAssembly file we use (they leave no trace in its contents). Until confirmed, the list is: list pending confirmation. We publish their license texts nonetheless.
libjpeg-turbo
JPEG images.
- Version
- to be confirmed
- License
- IJG License, BSD-3-Clause (zlib License for the SIMD code)
- Status
- list pending confirmation
- Full text
- libjpeg-turbo-LICENSE.txt · libjpeg-turbo-README.ijg.txt
Anti-Grain Geometry 2.3 (agg23)
Graphics rendering.
- Version
- 2.3
- License
- AGG 2.3 license (permissive)
- Copyright
- Copyright (C) 2002-2005 Maxim Shemanarev
- Status
- list pending confirmation
- Full text
- agg23.txt
Abseil
C++ utilities.
- Version
- to be confirmed
- License
- Apache-2.0
- Status
- list pending confirmation
- Full text
- abseil.txt
ICU
Text and character encodings (Unicode).
- Version
- to be confirmed
- License
- Unicode License v3
- Copyright
- Copyright (c) 2016-2025 Unicode, Inc.
- Status
- list pending confirmation
- Full text
- icu.txt
fast_float, simdutf, llvm-libc
fast_float, simdutf, and llvm-libc: three additional libraries from the PDFium reference build.
- Version
- to be confirmed
- License
- the one shown in the linked texts
- Status
- list pending confirmation
- Full text
- fast_float.txt · simdutf.txt · llvm-libc.txt
Emscripten (runtime, libc, libc++)
Supporting code added when compiling to WebAssembly (C and C++ standard library and utilities). Licenses are unconfirmed and full texts are not available.
- Version
- to be confirmed
- Status
- list pending confirmation
OCR PDF: text recognition
OCR PDF downloads the recognition engine and language models (Spanish and English) from this same website. Nothing is requested from external sites.
tesseract.js
JavaScript library managing text recognition.
- Version
- 7.0.0
- License
- Apache-2.0
- Copyright
- Copyright the tesseract.js authors
- Status
- confirmed by the package that distributes it
- Full text
- tesseract-js-LICENSE.txt
tesseract.js-core (Tesseract 5.1.0)
Tesseract 5.1.0 engine compiled to WebAssembly, in two variants of which your browser downloads one. Includes the invisible font used to render the text layer.
- Version
- 7.0.0
- License
- Apache-2.0
- Status
- confirmed by the package that distributes it
- Full text
- tesseract-js-core-LICENSE.txt
Leptonica
Image loading within Tesseract. Its license (2-clause BSD) is stated in package notices, but full text is not yet available.
- Version
- to be confirmed
- License
- BSD-2-Clause
- Status
- full license text still to be added
regenerator-runtime, buffer, ieee754, zlib.js
Small libraries bundled within tesseract.js: regenerator-runtime (MIT), buffer (MIT), ieee754 (3-clause BSD), and zlib.js (MIT). The linked file reproduces their copyright notices.
- Version
- to be confirmed
- License
- MIT; BSD-3-Clause (ieee754)
- Copyright
- Facebook, Inc. (regenerator-runtime); Feross Aboukhadijeh (buffer, ieee754); imaya (zlib.js)
- Status
- full license text still to be added
- Full text
- tesseract-js-bundled-notices.txt
tessdata_best (spa, eng)
“Best” integer-quantized recognition models for Spanish and English, as packaged by @tesseract.js-data/spa and @tesseract.js-data/eng 1.0.0 (packaging is MIT).
- Version
- 4.0.0_best_int
- License
- Apache-2.0 (packaging: MIT)
- Copyright
- Copyright the Tesseract OCR authors; packaging: Balearica / jeromewu
- Status
- confirmed by the package that distributes it
- Full text
- tesseract-models-LICENSE.txt
Fonts
Fonts on this website are served from this same website.
Noto Sans (subset)
A subset of Noto Sans (regular and bold; Latin, Greek and Cyrillic), served from this same site and embedded in PDFs when a tool adds text (page numbers, watermark).
- Version
- to be confirmed
- License
- SIL Open Font License 1.1
- Copyright
- Copyright 2015 Google LLC. All Rights Reserved.
- Status
- confirmed by the package that distributes it
- Full text
- noto-sans-OFL.txt
IBM Plex Sans, IBM Plex Mono
IBM Plex Sans (variable) and IBM Plex Mono, served from this same site.
- Version
- to be confirmed
- License
- SIL Open Font License 1.1
- Copyright
- Copyright © 2017 IBM Corp. with Reserved Font Name "Plex"
- Status
- confirmed by the package that distributes it
- Full text
- ibm-plex-OFL.txt
Proprietary code
The rest of the code for the website and tools is proprietary to Menzuri Gestión S.L. and includes no other third-party libraries beyond those listed on this page.