Credits

Humdrop stands on the shoulders of some generous open projects. Their inclusion doesn't imply that they endorse Humdrop.

Word lists: SCOWL by Kevin Atkinson, frequency data from wordfreq by Robyn Speer (the adapted word-list data is shared under CC BY-SA 4.0), and three-to-eight-letter entries from the Webster web2 list. The accepted list is built from SCOWL size 85, so the Australian English and UK Advanced Cryptics Dictionary notices apply too.
Analytics: the TelemetryDeck Swift SDK (MIT License). See the privacy policy for what it sends.
Font: Nunito by the Nunito Project Authors, under the SIL Open Font License 1.1. The game bundles Nunito Black, and this website serves a Latin subset of the same font from its own server (licence and notes).
Ads: the Google Mobile Ads and User Messaging Platform SDKs (Google's terms; Apache 2.0 package manifests). See the privacy policy for what ads mean for you.
Characters and art: the Humdrops, Maestro Hum, the Grumbles and everything else in the meadow are original Humdrop artwork.

Notices

The full notices, exactly as they appear in the game:

SCOWL

Humdrop's accepted word list is generated from SCOWL rel-2026.02.25, size 85 (American, British, Canadian and Australian spellings, variant level 6). It includes words from the UK Advanced Cryptics Dictionary and the Australian English data, so all three notices below apply. The SCOWL notice follows verbatim.

Permission to use, copy, modify, distribute, and sell any part of SCOWLv2, or word lists created from it, is hereby granted without fee, provided that the above copyright notice appears in all copies and that both the above copyright notice and this notice appear in supporting documentation. Kevin Atkinson makes no representations about the suitability of this database for any purpose. It is provided "as is" without express or implied warranty.

SCOWL is derived from many sources, most of which are in the Public Domain. Data from the Corpus of Contemporary American English (COCA) was also used.

All data from COCA comes from 3-gram data that is not freely available; however, the usage is within the rights given by the NDA that was signed when purchasing the data. More information on COCA is available at https://www.english-corpora.org/coca/.

The primary source of words for SCOWL comes from 12dicts and ENABLE2K. Both are in the Public Domain, but Alan Beale <biljir@pobox.com> deserves special credit as he is the author of 12dicts and a major contributor to ENABLE2K. In addition, he gave me an incredible amount of feedback and created a number of special lists in order to help improve the overall quality of SCOWL.

===

If you are using an official speller dictionary created by SCOWL that is not Australian English, then no additional copyright applies and including the notice before the === is sufficient.

If you are using the Australian English dictionary or a wordlist that uses the 'D' SPELLING code and/or the 'AU' REGION code, the copyright after '=== AU' applies.

If you are using a generated word list larger than 80, the copyright after '=== UKACD' applies.

If you are distributing the SCOWLv2 database or results from the SCOWL database that is not a speller dictionary or generated word list, then both copyrights may apply depending on the parts you use. In addition, the WordNet copyright MIGHT apply as WordNet was one of many sources used for the initial POS assignment.

=== AU

The initial information for Australian English comes from Benjamin Titze:

Permission to use, copy, modify, distribute and sell this array, the associated software, and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appears in all copies and that both that copyright notice and this permission notice appear in supporting documentation. Benjamin Titze makes no representations about the suitability of this array for any purpose. It is provided "as is" without express or implied warranty.

=== UKACD

Some words used come from the UK Advanced Cryptics Dictionary:

The following restriction is placed on the use of this publication: if The UK Advanced Cryptics Dictionary is used in a software package or redistributed in any form, the copyright notice must be prominently displayed and the text of this document must be included verbatim.

There are no other restrictions: I would like to see the list distributed as widely as possible.

Project: https://github.com/en-wl/wordlist

wordfreq

Humdrop's frequency ranks derive from the first 40,000 tokens generated from the "best" English list in wordfreq 3.1.1, created by Robyn Speer. The wordfreq software is available under Apache License 2.0. Its aggregated frequency data is distributed under Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0).

Humdrop modified the data by selecting eligible three-to-seven-letter entries, intersecting them with spelling sources, applying exact policy decisions and reviewed overrides, and assigning generation tiers. The adapted word-list data (the bundled Humdrop word lists, including the familiar word pool used for helpful deals and hints, and their source database) is distributed under CC BY-SA 4.0. No endorsement by Robyn Speer, wordfreq, or any source incorporated by wordfreq is implied.

Project and source notes: https://github.com/rspeer/wordfreq Data license: https://creativecommons.org/licenses/by-sa/4.0/ Software license: https://www.apache.org/licenses/LICENSE-2.0

Webster web2 word source

Humdrop's accepted word list includes entries from a modified snapshot of /usr/share/dict/web2 distributed with macOS, after removing its companion proper-name list and retaining lowercase ASCII entries of three to eight letters (an eight-letter derivative extends the earlier three-to-seven-letter validation layer). The system README identifies web2 as derived from Webster's Second International Dictionary and says the 1934 copyright "has lapsed, according to the supplier." The same README explains that FreeBSD maintains a list of current American English spellings rather than a historical document.

Humdrop makes no broader public-domain representation. Source identity, input hashes, filtering, and the exact supplier-qualified status statement are recorded in the project's vocabulary locks (Vocabulary/source-lock.json and Vocabulary/acceptance-source-lock.json) and its Webster notice.

Source README: https://github.com/freebsd/freebsd-src/blob/main/share/dict/README FreeBSD license: https://www.freebsd.org/copyright/freebsd-license/

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies, either expressed or implied, of the FreeBSD Project.

TelemetryDeck Swift SDK

Humdrop uses the TelemetryDeck Swift SDK 2.14.2 for anonymous usage counts. https://github.com/TelemetryDeck/SwiftSDK

Nunito (font)

Humdrop bundles Nunito Black (Nunito-Black.ttf, version 3.602, static instance from the official Google Fonts download of the Nunito family, https://fonts.google.com/specimen/Nunito; source project https://github.com/googlefonts/nunito). SHA-256 of the bundled file: 8de64ddb7d985763dd8dde658a9a2bb011f7509edcca475c02b281f4fe819e42.

This Font Software is licensed under the SIL Open Font License, Version 1.1. This license is copied below, and is also available with a FAQ at: https://openfontlicense.org

SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007

PREAMBLE
The goals of the Open Font License (OFL) are to stimulate worldwide development of collaborative font projects, to support the font creation efforts of academic and linguistic communities, and to provide a free and open framework in which fonts may be shared and improved in partnership with others.

The OFL allows the licensed fonts to be used, studied, modified and redistributed freely as long as they are not sold by themselves. The fonts, including any derivative works, can be bundled, embedded, redistributed and/or sold with any software provided that any reserved names are not used by derivative works. The fonts and derivatives, however, cannot be released under any other type of license. The requirement for fonts to remain under this license does not apply to any document created using the fonts or their derivatives.

DEFINITIONS
"Font Software" refers to the set of files released by the Copyright Holder(s) under this license and clearly marked as such. This may include source files, build scripts and documentation.

"Reserved Font Name" refers to any names specified as such after the copyright statement(s).

"Original Version" refers to the collection of Font Software components as distributed by the Copyright Holder(s).

"Modified Version" refers to any derivative made by adding to, deleting, or substituting -- in part or in whole -- any of the components of the Original Version, by changing formats or by porting the Font Software to a new environment.

"Author" refers to any designer, engineer, programmer, technical writer or other person who contributed to the Font Software.

PERMISSION & CONDITIONS
Permission is hereby granted, free of charge, to any person obtaining a copy of the Font Software, to use, study, copy, merge, embed, modify, redistribute, and sell modified and unmodified copies of the Font Software, subject to the following conditions:

1) Neither the Font Software nor any of its individual components, in Original or Modified Versions, may be sold by itself.

2) Original or Modified Versions of the Font Software may be bundled, redistributed and/or sold with any software, provided that each copy contains the above copyright notice and this license. These can be included either as stand-alone text files, human-readable headers or in the appropriate machine-readable metadata fields within text or binary files as long as those fields can be easily viewed by the user.

3) No Modified Version of the Font Software may use the Reserved Font Name(s) unless explicit written permission is granted by the corresponding Copyright Holder. This restriction only applies to the primary font name as presented to the users.

4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font Software shall not be used to promote, endorse or advertise any Modified Version, except to acknowledge the contribution(s) of the Copyright Holder(s) and the Author(s) or with their explicit written permission.

5) The Font Software, modified or unmodified, in part or in whole, must be distributed entirely under this license, and must not be distributed under any other license. The requirement for fonts to remain under this license does not apply to any document created using the Font Software.

TERMINATION
This license becomes null and void if any of the above conditions are not met.

DISCLAIMER
THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM OTHER DEALINGS IN THE FONT SOFTWARE.

Google Mobile Ads SDK and Google User Messaging Platform SDK

Humdrop uses the Google Mobile Ads SDK 13.11.0 and the Google User Messaging Platform SDK 3.1.0, distributed through Google's Swift packages: https://github.com/googleads/swift-package-manager-google-mobile-ads https://github.com/googleads/swift-package-manager-google-user-messaging-platform

The Swift package manifests are licensed under the Apache License, Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0). The SDK binaries are provided by Google LLC under Google's own terms: https://developers.google.com/admob/terms