ACT Rule 36b590 · proposed
Error message describes invalid form field value
When a form rejects what somebody typed, the message has to say what went wrong or how to put it right. "Invalid input" does neither. This rule reads the error text and asks whether it identifies the cause or the fix.
A tool can find the places this applies and then hand you the decision. The rule is proposed, so it has not yet been implemented in full by a tool and reviewed by a W3C working group, and the wording can still change.
What passing this rule proves
When this rule fails, 3.3.1 Error Identification is not satisfied, and that half is certain. When it passes, W3C's own outcome mapping says the criterion still needs further testing. So a green result here is evidence that one specific thing is not broken, and it is the answer W3C gives on 59 of its 87 live rules.
This is the only published rule for the whole of Guideline 3.3 Input Assistance, which covers nine criteria, and it is still proposed. Labels or Instructions, Error Suggestion, Error Prevention, Redundant Entry and Accessible Authentication have no rule at all. Forms are where most sites lose money, and they are where automated testing has the least to say.
The criteria this rule is a test for
These are the criteria the rule names as its own conformance requirement. Each one is a far bigger question than this rule asks, and our page for it sets out what the whole criterion covers.
- 3.3.1 Error Identification Level A
The normative rule text lives at W3C
What the rule applies to, and exactly what it expects, is published by W3C and can change. We link to it rather than restate it, so nothing here can quietly fall out of date against the source. Read rule 36b590 at W3C.
Error messages must identify which field failed and why
When a form is rejected, the message has to identify which field failed and what would fix it. Colour alone does not do it and neither does a red border.
Someone using a screen reader is not looking at the form. They need the problem named in text, tied to the field it belongs to.
A summary saying the form contains errors with nothing to say which field or why is the most common version. Users cannot tell what went wrong or how to fix it.
Fixes that satisfy it
If this rule fails on your site, these are the techniques that put it right.
All 87 ACT rules are grouped by the criteria they test, and 24 of them decide nothing about WCAG on their own. Run a free scan to see which of these your own pages trip.