Section 508 and WCAG: what each asks, and where they differ

WCAG is a technical standard. Section 508 is a US law that adopts it and adds more. If you build a web app and sell to US agencies, universities or public bodies, here is what each asks of you and where they differ.

Accessibility

WCAG: the standard

The Web Content Accessibility Guidelines are published by the W3C. The current version, 2.2, has 86 success criteria at three levels: A, AA and AAA. Level AA is what laws and contracts usually ask for. WCAG isn’t a law. It becomes a requirement when a law, a policy or a contract adopts it.

Section 508: the law that adopts it

Section 508 of the US Rehabilitation Act requires federal agencies to make the technology they build, buy and use accessible. Its current rules, the Revised 508 Standards, took effect in January 2018. They adopt WCAG 2.0 Level A and AA by reference, and go further in four ways.

Beyond the web. The same WCAG criteria apply to documents (PDFs, spreadsheets, slides) and installed software as well as websites. For documents and software, four criteria that only make sense on the web are left out: 2.4.1 Bypass Blocks, 2.4.5 Multiple Ways, 3.2.3 Consistent Navigation and 3.2.4 Consistent Identification.
Functional performance criteria (Chapter 3). At least one way to use the product without vision, with limited vision, without perceiving color, without hearing, with limited hearing, without speech, with limited manipulation, with limited reach and strength, and with limited language, cognitive and learning abilities. These apply where no technical criterion covers a feature.
Hardware and software (Chapters 4 and 5). For example, software must work with the platform’s assistive technology and respect the user’s settings for color, contrast, font size and focus cursor.
Documentation and support (Chapter 6). Help content must be accessible, and support services must be able to communicate with people who use assistive technology.

Side by side

Standard	Who it binds	Which WCAG
WCAG 2.2	No one on its own; whoever adopts it	2.2, A and AA in practice
Revised Section 508	US federal agencies, and the vendors selling to them	2.0 A and AA, plus Chapters 3 to 6
ADA Title II rule (2024)	US state and local governments, including public universities	2.1 A and AA for web content and mobile apps
EN 301 549	Public bodies in the EU, and products under the European Accessibility Act	2.1 A and AA, plus requirements beyond the web

Many US states and universities write their own policies, usually naming Section 508 or a version of WCAG at Level AA. Check which one the request names.

What this means for a web app

WCAG versions build on each other. WCAG 2.2 AA includes every 2.0 and 2.1 AA criterion except 4.1.1 Parsing, which 2.2 retired. Meeting 2.2 AA covers the WCAG criteria all four standards above ask of web content, except that one row. EN 301 549 also has clauses that reach past the page, such as documentation and support. A 508 or EN 301 549 report still lists 4.1.1, so answer it with valid markup or the W3C’s note that browsers now handle it.
A Section 508 report asks about more than the web pages: the functional performance criteria, your help content and your support. Have an answer for each before the request arrives.
In a VPAT, use the 508 edition for US federal requests, the EU edition for EN 301 549, and the INT edition when you sell in more than one market. Read and write an accessibility conformance report

See it on a product