Why is empty alt text a problem?

An image with empty alt text like ![](photo.png) is announced by screen readers as just "image" or the filename, giving no context. Meaningful alt text describes the image, while a truly decorative image should use an explicit empty alt with a comment explaining the intent.

What is a skipped heading level?

Heading levels should increase by one at a time. Jumping from an H2 straight to an H4 skips H3, which breaks the document outline that screen-reader users navigate by. The checker flags any heading that is more than one level deeper than its predecessor.

Why are bare URLs flagged?

A bare URL like https://example.com/page?id=42 becomes the link text itself, which screen readers read out character by character. Descriptive link text such as [pricing page](…) is far clearer and more accessible.

Does it modify my Markdown?

No. The tool only reads and reports. It never rewrites your content, and everything is processed locally in your browser.

Does a clean result guarantee full accessibility?

No. These are common, high-impact Markdown-level issues, but full accessibility also depends on colour contrast, reading order, and the rendered HTML. Treat a clean result as a strong baseline, not a complete WCAG audit.

Markdown Accessibility Checker

Markdown is the writing format behind most documentation, READMEs, and technical blogs, but it is easy to ship content that is inaccessible once it renders to HTML. Missing alt text, headings that jump levels, and raw URLs all create real barriers for screen-reader users. This checker scans your Markdown source in the browser and flags those issues line by line so you can fix them before publishing.

How it works

The tool walks your Markdown one line at a time and applies four rules:

Empty alt text — image syntax ![](url) with nothing between the brackets is flagged, because the image has no text alternative.
Skipped heading levels — it tracks the current ATX heading depth (the number of leading # characters) and flags any heading that is more than one level deeper than the previous one.
Bare URLs — a line containing a raw http(s):// link that is not already wrapped in [text](url) link syntax is flagged, since it will render as unreadable link text.
Header-less tables — a pipe table whose first row is not followed by a |---| separator row is flagged, because it lacks the header row that assistive tech relies on.

Each finding shows the line number and the offending text so you can jump straight to it.

Tips and example

Consider this snippet:

## Overview
#### Details
![](diagram.png)
See https://example.com/specs for more.

The checker reports three issues: the #### heading skips H3, the image has empty alt text, and the bare URL should be [the specs](https://example.com/specs). A fixed version uses a ### heading, ![Architecture diagram](diagram.png), and descriptive link text — clean across all four rules.