Image Validation
A broken image URL, missing alt text, or oversized file won’t announce itself during build. It shows up after you hit send in a broken layout, a slow load, or an accessibility complaint. Mailgun Inspect catches those issues before they reach a single subscriber.
Pre-send image checks
Broken images don’t just look bad. They signal to subscribers that something went wrong. Missing alt text shuts out screen reader users. Oversized files slow load times across every device. Image validation adds automated checks to your pre-send QA so you fix issues before they reach inboxes.
Flag broken image URLs before they affect the email experience
Catch missing alt text before accessibility gaps reach subscribers
Identify oversized images that slow email loading
Review total email weight and load time and automatically compress images to improve performance
Spot missing width and height attributes before layout shifts happen
Better Email QA
Mailgun Inspect parses your full email HTML, finds every image tag, and runs three checks per image: URL validation, alt text presence, and file size measurement.
Results come back as a JSON report with per-image details including url, alt_text_present, file_size_kb, and is_broken, plus total email weight and load time.
Flag and fix issues
Submit your email for review by pasting HTML, providing a hosted URL, or sending to a Mailgun-generated address. Filter results by severity or issue type. Export as a PDF or pull the API response into your own tooling.
Run image validation through the Inspect UI or via API
Filter issues by severity or issue type to focus review on what matters
Export results as a PDF or use the API response in your own reporting workflow
Get Started
Run tests using Mailgun Inspect three ways by sending from your ESP, pasting your HTML directly, or uploading from a URL. Or you can use the API to run an image validation check to retrieve results via a JSON response.
Mailgun Inspect runs automated checks for common issues – including image validation. Flagged issues can be found in the dashboard.
Once you’ve identified the issues, you can easily resolve them before you hit send.
FAQs
Email image validation checks every image referenced in an email before it’s sent. It confirms URLs resolve, file sizes are reasonable, and alt text is present. Mailgun Inspect runs these checks directly from your email HTML.
Inspect checks three things per image: whether the URL is broken, whether alt text is present, and the file size in KB. It also reports total email weight and load time.
Inspect reports file_size_kb for each image so you can identify files that may slow loading. It can also automatically compress images where possible to improve performance.
With Mailgun, the maximum size for a single email message including content, headers, and attachments is 25 MB. However, many inbox providers have their own incoming message size limits. Email experts recommend keeping the entire HTML email under 100-500 KB.
Yes. Inspect offers both a UI and a full API with identical feature coverage. Results can also be exported as a PDF for sharing outside the platform.
Dimension optimization means setting explicit width and height attributes on image elements in HTML. It prevents layout shifts during loading by letting the email client allocate space before the image renders.
