Free icon sets are icon collections published under open-source licences, and the licence file in each project states what is allowed. The popular libraries use short permissive licences: MIT, ISC or Apache.
This guide compares those licences and how they apply to icons on websites. It is one part of the wider topic of free graphic design resources, and it is independent information with no affiliation to any icon project or its authors.
The three licences behind most open-source icon libraries
Open-source icon libraries are distributed like software, and most of them reuse one of three well-known licences. Reading the licence file in the repository is the reliable way to learn which applies, because the file is the legal text and a README or a website only describes it.
| Icon library | Licence named in its repository LICENSE file |
|---|---|
| Heroicons | MIT License |
| Feather | The MIT License (MIT) |
| Lucide | ISC License |
| Bootstrap Icons | The MIT License (MIT) |
| Tabler Icons | MIT License |
| Phosphor Icons | MIT License |
| Material Design Icons (Google) | Apache License Version 2.0, January 2004 |
The licence names above are taken from the LICENSE files of the Heroicons repository and the Material Design Icons repository, with the other projects’ files read the same way. A project can change its licence in a later release, so the file in the version being installed is the one to read.
What the MIT licence asks of a site owner
The MIT licence is the most common choice in the table. Its grant is broad: permission is given “to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software” free of charge. Using icons on a commercial website falls inside that grant, and so does editing an icon’s paths to match a brand.
The single condition is a notice requirement: “The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.” For the Bootstrap Icons licence, the copyright line names The Bootstrap Authors, and the Tabler Icons licence names its own author. In practice, shipping the licence text in a project’s licence or third-party notices file satisfies the condition for a site that bundles the icon files.
The licence also carries a disclaimer: the software “is provided” as is, without warranty of any kind. Icons come with no guarantee that they fit a project, render identically everywhere or remain maintained.
ISC and Apache compared with MIT
The ISC licence used by Lucide is shorter and works the same way. It grants “Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee”, provided “that the above copyright notice and this permission notice appear in all copies.” For a site owner, the routine is identical to MIT: keep the notice with the files.
The Apache licence, used by the Material Design icons repository, is longer. Its copyright grant gives a “perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Work”. The licence adds conditions for redistribution: recipients of the Work must receive a copy of the licence, and modified files must carry prominent notices stating that they were changed.
The Apache licence also contains a patent grant, which MIT and ISC do not spell out. Each contributor grants “a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license”, and the same section says that if a user starts patent litigation alleging that the Work infringes a patent, the patent licences granted to that user for the Work end. For icon artwork this clause rarely matters, but it is one reason companies with formal licence policies sometimes prefer Apache-licensed material.
The Apache licence includes a stronger statement on responsibility as well. It says the licensor provides the Work “on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND”, and that the user is solely responsible for determining the appropriateness of using or redistributing the Work. Whichever licence a library uses, the decision to rely on the icons stays with the site owner.
The practical difference is the edit trail. A designer who changes Apache-licensed icon files and passes them on needs to mark which files were changed. The other two licences in the table only ask for the notice to stay with the files.
Using icons without breaking the licence
Most mistakes come from treating the licence as a statement about the artwork alone. A few habits prevent them.
- Keep the licence text. Store the LICENSE file from each icon package alongside the project’s other third-party notices.
- Record the source and version. Note the package name, version and repository address, because a licence can differ between releases.
- Keep the notice if you redistribute. The MIT and ISC texts allow redistribution and sale as long as the copyright notice and permission notice travel with each copy, so a republished icon pack must carry them. Project names and logos are a separate matter: the Apache licence, for one, states that it “does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor”.
- Mark edits where the licence asks. Under the Apache licence, modified files carry notices stating the change.
- Treat logos separately. A brand logo inside an icon pack may be covered by a trademark that the software licence does not address.
Those habits apply to every asset type on a project. Photographs follow a different set of rules, explained in the guide to free stock photos, and presentation files such as psd mockups are covered by licences that creators write for themselves.
Reading a licence file in a minute
A licence file looks long, but three questions cover most of it. The first is what the grant allows: look for the verbs “use, copy, modify” and whether selling or sublicensing is mentioned. The second is what must travel with the files: the MIT and ISC texts require the copyright notice and permission notice, and the Apache licence requires a copy of the licence, plus change notices on modified files. The third is what the author disclaims: every licence in the table includes a warranty disclaimer.
The notice lines name the rights holder, which is useful when a site’s legal page lists third-party components. The Heroicons file names Tailwind Labs, Inc., the Feather file names Cole Bemis, the Lucide file names Lucide Icons and Contributors, and the Phosphor file names Phosphor Icons. Listing the library name and licence in a site’s notices file is enough to keep the record complete.
Choosing between libraries
The licence rarely decides the choice among MIT, ISC and Apache libraries, since all permit free use on websites. The decision usually rests on the design style, the number of icons, the file formats supplied and how actively the project is maintained. Those points are best checked on the project’s own repository page, where releases and recent activity are visible.
Consistency matters more than variety. Mixing two sets with different stroke widths or corner styles makes an interface look uneven, and it also doubles the licence files to track. A single library chosen early, with its licence recorded, keeps both the design and the paperwork simple.
One caveat applies to every set: the licence file in a repository covers the project’s own material. Where a project bundles artwork from another source, that artwork may carry its own terms. Reading the README sections on credits and third-party content is part of the same due diligence.
Frequently asked questions
Can open-source icons be used on commercial websites?
The MIT licence grants permission to use, copy, modify, merge, publish, distribute, sublicense and sell copies of the software, which covers commercial use. The ISC and Apache licences also allow use, with their own notice conditions.
Is credit on the page required for MIT icons?
The MIT condition is that the copyright notice and permission notice are included in all copies or substantial portions of the software. Keeping the licence text with the bundled files meets it; the licence does not ask for a visible credit line on each page.
Can an icon be edited to match a brand colour?
The MIT, ISC and Apache licences all allow modification. The Apache licence additionally requires modified files to carry prominent notices stating that they were changed.
Do the licences promise that the icons are free of defects?
No. The MIT licence states that the software is provided as is, without warranty of any kind.
