Accessibility Heatmap Generator

Generate a contrast-focused accessibility heatmap from a UI screenshot or HTML input and suggest stronger patch colors

Upload a UI screenshot or paste HTML with inline colors, then generate a heatmap that highlights regions likely to fail WCAG contrast thresholds. The tool is designed for quick visual triage before design review or implementation handoff.

How it works:

  • For screenshots, it samples local color tiles, estimates contrast hotspots, and renders a red overlay heatmap.
  • For HTML, it inspects inline foreground/background pairs and returns low-contrast findings plus suggested patch colors.
  • WCAG Level controls the threshold: AA uses 4.5:1 and AAA uses 7:1 for normal text.
  • Show Patch Suggestions adds recommended foreground color values to help lift contrast faster.

Example Results

1 examples

Generate a heatmap from a low-contrast dashboard screenshot

Highlight UI regions likely to fail AA/AAA and attach suggested patch colors for faster design iteration.

accessibility-heatmap-example-report.html View File
View input parameters
{ "htmlInput": "", "designImage": "/public/samples/images/logo.png", "wcagLevel": "AA", "showPatchSuggestions": true }

Click to upload file or drag and drop file here

Maximum file size: 15MB Supported formats: image/png, image/jpeg, image/webp, .png, .jpg, .jpeg, .webp

Key Facts

Category
Design & Color
Input Types
textarea, file, select, checkbox
Output Type
file
Sample Coverage
4
API Ready
Yes

Overview

The Accessibility Heatmap Generator is a visual triage tool that evaluates UI screenshots or HTML code to identify contrast issues. By highlighting regions that fail WCAG AA or AAA thresholds with a red overlay, it allows designers and developers to quickly spot accessibility risks before implementation. It also provides actionable patch suggestions to help you easily lift contrast ratios to compliant levels.

When to Use

  • •When reviewing design mockups to catch low-contrast text before handing files off to developers.
  • •When auditing existing HTML components to ensure inline foreground and background colors meet WCAG standards.
  • •When you need quick, actionable color adjustments to fix accessibility failures without manually calculating contrast ratios.

How It Works

  • •Upload a UI screenshot (PNG, JPG, WEBP) or paste an HTML snippet containing inline color styles.
  • •Select your target WCAG compliance level (AA for 4.5:1 or AAA for 7:1) to set the strictness of the contrast check.
  • •Enable 'Show Patch Suggestions' to automatically generate recommended foreground colors that pass the selected threshold.
  • •Download the generated HTML report, which displays a red overlay heatmap on images or lists specific contrast findings for HTML inputs.

Use Cases

Designers validating dashboard mockups to ensure gray text on white backgrounds remains legible for visually impaired users.
Front-end developers testing HTML email templates to verify that inline styles meet accessibility guidelines.
QA testers performing visual accessibility audits on web applications by taking screenshots of various UI states.

Examples

1. Auditing a Dashboard Mockup

UI Designer
Background
A designer is preparing to hand off a new analytics dashboard to the engineering team but wants to ensure the color palette is accessible.
Problem
Manually checking every text element's contrast against its background using a color picker is tedious and prone to human error.
How to Use
Upload the dashboard screenshot, set the WCAG Level to 'AA', and enable 'Show Patch Suggestions'.
Example Config
WCAG Level: AA, Show Patch Suggestions: true
Outcome
The tool generates a heatmap with red overlays on low-contrast labels and provides alternative hex codes to fix the failing elements.

2. Fixing Inline HTML Component Colors

Front-end Developer
Background
A developer is building a promotional banner using inline HTML styles, but the marketing team reported that the text is hard to read.
Problem
The developer needs to quickly identify which inline color pairs fail WCAG AAA standards and find compliant alternatives.
How to Use
Paste the HTML snippet into the 'HTML Input' field, select 'AAA' for the WCAG Level, and run the generator.
Example Config
WCAG Level: AAA, Show Patch Suggestions: true
Outcome
An HTML report is produced detailing the exact failing foreground/background pairs along with suggested color values that meet the 7:1 ratio.

Try with Samples

html, image, png
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FAQ

What image formats are supported?

You can upload PNG, JPG, or WEBP images up to 15MB for screenshot analysis.

What is the difference between WCAG AA and AAA?

WCAG AA requires a contrast ratio of at least 4.5:1 for normal text, while AAA is stricter and requires a 7:1 ratio.

How does the tool analyze HTML?

It inspects inline style attributes for foreground and background color pairs, calculates their contrast ratio, and flags those that fail the selected WCAG level.

What are patch suggestions?

If enabled, the tool calculates and recommends a new foreground color that is visually similar but dark or light enough to pass the contrast threshold.

Can it analyze an entire live website?

No, the tool is designed for specific UI screenshots or raw HTML snippets to provide focused, component-level triage.

API Documentation

Request Endpoint

POST /en/api/tools/accessibility-heatmap-generator

Request Parameters

Parameter Name Type Required Description
htmlInput textarea No -
designImage file (Upload required) No -
wcagLevel select No -
showPatchSuggestions checkbox No -

File type parameters need to be uploaded first via POST /upload/accessibility-heatmap-generator to get filePath, then pass filePath to the corresponding file field.

Response Format

{
  "filePath": "/public/processing/randomid.ext",
  "fileName": "output.ext",
  "contentType": "application/octet-stream",
  "size": 1024,
  "metadata": {
    "key": "value"
  },
  "error": "Error message (optional)",
  "message": "Notification message (optional)"
}
File: File

AI MCP Documentation

Add this tool to your MCP server configuration: 

{
  "mcpServers": {
    "elysiatools-accessibility-heatmap-generator": {
      "name": "accessibility-heatmap-generator",
      "description": "Generate a contrast-focused accessibility heatmap from a UI screenshot or HTML input and suggest stronger patch colors",
      "baseUrl": "https://elysiatools.com/mcp/sse?toolId=accessibility-heatmap-generator",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

You can chain multiple tools, e.g.: `https://elysiatools.com/mcp/sse?toolId=png-to-webp,jpg-to-webp,gif-to-webp`, max 20 tools.

Supports URL file links or Base64 encoding for file parameters.

If you encounter any issues, please contact us at [email protected]