Search engines and screen readers both consume a page without seeing it, so structure, text alternatives and meaningful link text serve both. The overlap is real and it is not total, which is worth being precise about.

Why they overlap at all

A screen reader and a search crawler have the same fundamental constraint: neither can look at your page.

Both work from the markup, the text, and the structural relationships between them. Both depend on you having said what things are rather than only made them look like something.

Which means work done for one frequently serves the other, and it is worth understanding where that holds and where it does not.

The genuine overlaps

Heading structure

Headings tell a screen reader user how a page is organised and let them jump. They also communicate the page's structure and subject to a search engine.

Text made large and bold does neither. Real headings in a sensible order do both.

Link text

Click here is useless in a screen reader's link list and tells a search engine nothing about the destination.

Descriptive link text is one of the clearest cases where a single change serves both audiences fully.

Text alternatives for images

Alternative text is what a screen reader announces and one of the few signals a search engine has for understanding an image.

Written for the reader it serves both. Written for search it serves neither, which is the recurring lesson.

Content that exists as text

A price list in an image, a menu in a document, a diagram carrying the argument. Invisible to assistive technology and invisible to search, for the same reason.

Captions and transcripts

Required for video to be usable by people who cannot hear it, and the only way the words in a video become text anything can read.

Clear, well-structured writing

Easier to understand for a struggling reader, and easier for a system trying to determine what the page answers.

Where the overlap stops

Worth being precise, because the claim gets overstated.

Colour contrast does nothing for search. Neither does focus indication, keyboard operability, motion preferences, or touch target size.

Those are substantial parts of accessibility work with no search benefit whatsoever, and they matter anyway.

Conversely, plenty of search work has no accessibility dimension: internal linking strategy, page speed on a fast connection, structured data markup, and how you organise your address structure.

So the honest statement is that the overlap is substantial and partial. Accessibility is not an SEO tactic, and treating it as one leads to doing the half that overlaps and stopping.

The asymmetry worth knowing

Search engines are more forgiving than assistive technology.

A crawler can frequently infer structure a screen reader cannot, because it has more context and is guessing at scale rather than reading aloud to one person in real time.

Which means a page can rank perfectly well while being genuinely difficult to use, and this is common. Ranking is not evidence of accessibility.

The reverse is closer to true: a page built properly for assistive technology is nearly always well formed for a crawler, because the requirements are stricter in the same direction.

That asymmetry is the practical reason to lead with accessibility rather than with search. Doing the harder one well tends to satisfy the easier one.

The one that is neither

Worth naming because it comes up.

Accessibility overlays do nothing for search, since they operate after the page loads and change nothing a crawler sees. They are also broadly rejected by the accessibility community.

A supplier presenting an overlay as improving both is describing something that does neither.

How to use the overlap

Practically, if you are trying to justify the work internally.

The shared items are the easiest to fund, because they have two returns and one cost. Headings, link text, text alternatives, real text instead of images, and transcripts.

Start there, and the accessibility-only items become easier to argue for afterwards, because the site is already partway and the remaining list is shorter than it was.

The argument for the whole of it, rather than the overlapping half, is set out in why accessibility is a business issue.

Frequently asked questions

Why do accessibility and search overlap?

Screen readers and search crawlers share a constraint: neither can see the page. Both work from markup, text, and structural relationships.

Which items serve both?

Heading structure, descriptive link text, text alternatives for images, content existing as real text, captions and transcripts, and clear writing.

Where does the overlap stop?

Colour contrast, focus indication, keyboard operability, motion preferences and touch target size do nothing for search, and matter anyway.

Does ranking well mean a site is accessible?

No. Crawlers are more forgiving and can infer structure a screen reader cannot, so a page can rank perfectly well while being difficult to use.

Which direction is more reliable?

A page built properly for assistive technology is nearly always well formed for a crawler, because the requirements are stricter in the same direction.

How should I use the overlap?

Start with the shared items, which have two returns and one cost. The accessibility-only work is easier to argue for once the site is partway there.

West Coast Media Solutions Inc. provides web design, web development, hosting, digital marketing, and business consulting to organisations across Canada, drawing on more than twenty-five years in the field.

Trying to justify accessibility work internally?

We usually start with the items that serve search too, which shortens the list that needs arguing for on its own.

Start a Conversation