4.5:1 for normal text, 3:1 for large text: what the contrast requirement means in a PDF, when logos and decoration are exempt, why text in artefacts is a special case – and how to measure reliably.
WCAG 1.4.3 (Contrast (Minimum), level AA) requires a contrast ratio of at least 4.5:1 against the background for text and images of text; for large text – from 18 point, or from 14 point in bold – 3:1 is sufficient. Text in logos and brand names is exempt, as is ‘incidental’ text, such as pure decoration. For PDFs, the requirement applies via chapter 10 of EN 301 549, the European standard on accessibility requirements for ICT (requirement 10.1.4.3). PDF/UA itself does not regulate contrast: a PDF can pass every PDF/UA check and still be too pale for many people.
What the contrast ratio is
The ratio compares the relative luminance of the lighter colour with that of the darker colour; it ranges from 1:1 (same colour) to 21:1 (black on white). A few shades of grey on a white background for orientation:
Contrast ratios of selected shades of grey on white| Text colour on white | Contrast | Sufficient for |
|---|
| #595959 (dark grey) | 7.0:1 | any text |
|---|
| #767676 (medium grey) | 4.54:1 | any text, only just |
|---|
| #949494 (light grey) | 3.03:1 | large text only |
|---|
| #999999 (light grey) | 2.85:1 | no text |
|---|
The popular light greys for footnotes, source references and captions in particular are often below 4.5:1.
What counts as large text
Large text starts at 18 point, or at 14 point in bold. What matters is the font size in the document, not the zoom level at which someone views it. Narrow or very thin typefaces look smaller than their point size suggests – if you are close to the threshold, apply the higher value.
The exceptions
- Logos and brand names: text that is part of a logo or brand name has no contrast requirement. The logo of the funding programme or the town’s word mark do not have to be recoloured.
- Incidental text: text that is pure decoration, that is not visible, or that is part of an image containing significant other visual content – such as a street sign in a photo.
- Not an exception: slogans in corporate colours in running text, coloured table headers, text on cover images that carries information, and images of text such as scanned posters.
Special case: text in artefacts
Artefacts are content without meaning of its own: recurring running headers and footers, page numbers, decoration. Checking tools such as PAC usually do not include text in artefacts in the contrast measurement. However, WCAG does not exempt ‘text in artefacts’, but pure decoration. Two rules follow from this:
- A pale page number in the footer is not a problem; contact details, file references or a validity date in the same footer are – they need sufficient contrast.
- Marking text as an artefact to make the contrast warning disappear is doubly wrong: for screen reader users the text is then gone, and for people with visual impairments it remains hard to read.
What does not fall under 1.4.3 but belongs with it
- Use of Color (WCAG 1.4.1): information must not be conveyed by colour alone – for example negative amounts only in red, or required fields marked only by colour.
- Non-text Contrast (WCAG 1.4.11): graphical elements needed for understanding – chart lines, map symbols, borders of form fields – need at least 3:1 against their surroundings.
How to measure
- Take colour values from the source: design template, Word style, corporate design manual. Exact values are better than any on-screen measurement.
- Measure with a contrast tool: for example the free Colour Contrast Analyser. Click the eyedropper inside a letter, not on its edge – there, anti-aliasing mixes text and background colour.
- Text on photos and gradients: measure at the least favourable point, i.e. where the background is most similar to the text.
- Transparency and overlays: measure the colour actually displayed, not the one that was set.
- Have it checked automatically: tools measure text on a plain background reliably; for text on images and gradients, their results are only an indication.
Improve it in the source document or in the PDF?
Ideally in the source document: changing a colour in the style affects every future output. In the finished PDF, text that is too light can be darkened automatically. This slightly changes the appearance and should therefore be a conscious decision – especially when a corporate design is involved. Logos are left untouched.
Common mistakes
- Light grey footnotes, source references and captions.
- White text on a light photo or a pastel-coloured area.
- White text in table headers with medium-light green or orange.
- Measuring at the edge of a letter instead of inside it.
- Content is marked as an artefact to make the warning disappear.
- Red text is the only sign of a negative value.
How DokAudit helps
Contrast is not one of the rules veraPDF checks. DokAudit therefore measures it itself: text on a light background is checked against 4.5:1 and 3:1, text in artefacts does not count, logos and brand names are exempt. Very light or white text usually sits on coloured areas whose colour cannot be determined reliably without rendering; it is therefore left out, and the report recommends measuring text on coloured areas by hand if in doubt. On request, the ‘Improve colour contrast’ switch automatically darkens text that is too light until it reaches 4.5:1; the test report lists every changed colour with its old and new value. The switch is off by default. A real-life example is shown in the case study on the urban development plan.
Sources:
As of: 10/2026. This article gives a general overview and is not legal advice. The legal and standards texts in force are authoritative; in individual cases, the law of the German states (Länder) may differ.