Crawvix Image Doctor Explained: What It Checks and How to Fix Each Finding

Image Doctor is the Crawvix feature that lists the images used across your website and checks them for common problems: missing alt text, files that do not load, very large files, missing width and height, a lazy-loaded image near the top of a page, and more. It reads your website and reports what it finds, with the evidence and what to do next. It never changes your site, and it does not compress or edit your pictures.

This guide is for site owners and developers. You will learn how to run it, how to read the list, and what each finding means, why it matters and how to fix it. Image Doctor is included in every Crawvix plan; see pricing for the plans and the Image Doctor page for a short overview.

Before you begin

You will need:

A Crawvix account with the website added and its ownership verified.
A Crawvix plan that includes full scans. Image Doctor is not available for the free website sample.
Access to where you edit pages and media.

Image Doctor only reads, so running it carries no risk. The risk is in the fixes, so keep the originals and replace images one at a time.

What Image Doctor is

After a full scan, Crawvix builds a list of the images written into the HTML of the pages it read. It looks at img elements, picture sources, srcset lists, lazy-loading attributes and the base href, which changes how relative addresses are read. The list holds up to 2,000 unique images. Each entry is one image address, with every page that uses it and the alt text each page gives it.

Image Doctor then asks the server about some of them. It sends HEAD requests, a kind of web request that returns the status, content type and file size without the picture itself, for up to 200 images. It does this politely: it honours robots.txt on the site's own host and makes at most 10 requests to any other host, such as a CDN. It never downloads or stores the pictures.

CSS background images and images drawn by scripts are not listed. Image Doctor does not compress or edit images and does not promise rankings. Suggested alt text, written for you to review, is planned (the Alt Text Writer) but not available yet.

How to run Image Doctor

Step 1: Verify your website

Add your site in Crawvix and complete the ownership check. Image Doctor works only on verified sites.

What success looks like: the site shows as verified.

Step 2: Run a full scan

Start a full scan. A full scan reads many pages, which is what gives Image Doctor a real list.

What success looks like: the scan completes and the site shows results.

Step 3: Open the Images tab

On the website's page, open the Images tab, next to Broken links.

What success looks like: you see images listed with their findings.

How to read the list

Each row is one image address. Open a row to see every page that uses it and its alt text on each. A file used on twenty pages is one entry, so one fix can clear many pages.

You can filter by finding and by severity, search, and export the list as a CSV file for a spreadsheet or a developer. Each finding links to the matching scan check.

Label	Meaning	How to treat it
Problem	Clearly wrong or very likely to matter.	Fix first.
Review	May be fine or may need work; a person has to judge.	Look at each item and decide.
Advice	A suggestion that could improve the image.	Fix when convenient.

Review items are not definite failures. Generic alt text and different alt texts for one image are only ever review items.

Finding: no alt attribute

What it means. An img element has no alt attribute at all. This is a problem-level finding. A purposely empty alt="" on a decorative image is correct and is not flagged.

Why it matters. Without alt text, some assistive technology reads out the file name. Search engines also use alt text as one signal about what an image shows.

How to fix it. Add a short description of what the image shows in context, or an empty attribute if it is purely decorative.

<img src="/img/team.jpg" width="800" height="533"
     alt="Four members of the support team at their desks">

<img src="/img/divider.svg" width="600" height="20" alt="">

In a CMS, fill in the alt field in the media library or image settings. See Image SEO: Alt Text, File Names and Formats That Help Search.

Finding: generic alt text

What it means. The alt text exists but says very little, such as "image", "photo" or a file name. This is a review item, because only a person can judge whether a short alt text is enough in context.

Why it matters. Alt text that does not describe the image gives screen reader users and search engines little to work with.

How to fix it. Describe what matters about the image in that place on the page. Skip phrases like "image of", since assistive technology already announces an image.

For example, alt="Blue ceramic mug on a wooden table" is better than alt="image".

Finding: the same image with different alt text on different pages

What it means. One image address is used on several pages with different alt text. This is a review item. The difference can be correct if the image plays different roles.

Why it matters. Sometimes it is accidental, such as one editor writing a description and another leaving a placeholder.

How to fix it. Open the row and compare the pages. If the role is the same everywhere, make the text match. If the role differs, keep the different text.

Finding: image does not load

What it means. The server answered with a 404 (not found), a 410 (gone) or a server error, or the request failed.

Why it matters. Visitors see a broken picture or empty space.

How to fix it. Open the address in a browser to confirm. If the file was moved, update the page or restore the file. If it was deleted on purpose, remove the image from every page the row lists. For a server error, check the server or CDN, since a temporary fault can show up as a failure. See Find Broken Internal Links and Redirects Across Your Website.

Finding: address does not return an image

What it means. The address answered, but the content type was not an image. It may be an HTML page, a login screen or an error page. This is a review item.

Why it matters. The image shows as broken. It can also mean a hotlink rule or firewall is blocking the request.

How to fix it. Open the address in a browser. If it shows a page, correct the path or the rule returning the wrong content. Some servers answer automated requests differently from browsers, so check by hand first.

Finding: large file

What it means. The server reports a file size from 300 KB, which is a review item, or from 1 MB, which is a problem. This applies only to pictures Image Doctor actually asked about, up to 200 of them.

Why it matters. Large files take longer to download, especially on mobile connections, and a large image near the top of a page can delay the Largest Contentful Paint. The Core Web Vitals "good" thresholds, at the 75th percentile, are LCP at or under 2.5 seconds, CLS at or under 0.1 and INP at or under 200 milliseconds.

How to fix it. Resize the picture to about the largest size it is shown at, compress it and consider a modern format..

See Fix Largest Contentful Paint (LCP) on Mobile.

Finding: no width and height

What it means. The image element has no width and height attributes (review).

Why it matters. Without them the browser may not know how much space to reserve, so text below can jump when the image arrives. That jump counts toward Cumulative Layout Shift.

How to fix it. Add the image's real pixel dimensions. CSS such as height: auto can still scale it.

<img src="/img/team.jpg" width="800" height="533" alt="Support team at their desks">

See Reduce Cumulative Layout Shift (CLS) Step by Step.

Finding: one of the first two images loads lazily

What it means. One of the first two images on a page has loading="lazy". This is a review item, because the first images are often, though not always, visible when the page opens.

Why it matters. Lazy loading suits pictures far down the page, but for a picture visible on arrival it can delay the largest element on screen.

How to fix it. If the image is visible without scrolling, remove the lazy attribute and consider a high fetch priority for the main one.

<img src="/img/hero.webp" width="1600" height="800" alt="Greenhouse interior with rows of herbs"
     fetchpriority="high">

Keep loading="lazy" further down. See Lazy Loading Images for SEO: Defer Images Without Hiding Them.

Finding: a newer format would be smaller

What it means. Image Doctor has a measured size for the file, and a newer format such as WebP or AVIF would typically be smaller. This is advice, and it appears only with a measured size.

Why it matters. Smaller files download faster, though the saving depends on the image.

How to fix it. Export the picture in a newer format and compare quality and size. Check current browser support at caniuse.com, and keep a fallback with the picture element where you need one.

<picture>
  <source srcset="/img/photo.avif" type="image/avif">
  <source srcset="/img/photo.webp" type="image/webp">
  <img src="/img/photo.jpg" width="1200" height="800" alt="Harbour at sunrise">
</picture>

See Use WebP and AVIF Images to Improve Website Speed.

Finding: no smaller versions for small screens

What it means. The image offers no smaller alternatives, so every device receives the same file. This is advice, shown only with a measured size.

Why it matters. A phone does not need a file built for a wide desktop screen.

How to fix it. Create several widths and list them in srcset, with a sizes attribute describing how wide the image appears.

<img src="/img/photo-800.webp"
     srcset="/img/photo-400.webp 400w, /img/photo-800.webp 800w, /img/photo-1600.webp 1600w"
     sizes="(min-width: 800px) 50vw, 100vw"
     width="1600" height="1000" alt="Workshop table with tools">

Many CMS platforms generate these for you. See Responsive Images with srcset and sizes: Serve the Right Size.

Finding: generic file name

What it means. The file name looks like a camera or editor default, such as IMG_4021.jpg or image1.png. This is advice.

Why it matters. A descriptive file name is a small signal and makes your media library easier to manage. It matters less than alt text and file size.

How to fix it. Use lowercase words separated by hyphens, such as blue-ceramic-mug.webp. Renaming creates a new address, so update every page that uses the image and redirect the old address if other sites link to it.

Step-by-step instructions

Fix findings in order of impact, not in the order they appear.

Step 1: Fix images that do not load, and addresses that are not images

Visitors see these directly, and one fix often clears many pages.

What success looks like: every broken address is restored, replaced or removed.

Step 2: Add missing alt text

Handle the problem-level findings first, and mark decorative images with alt="".

What success looks like: the no-alt findings are cleared.

Step 3: Shrink the largest files

Work down from the problem-level large files, starting with images near the top of pages.

What success looks like: your biggest images are well under 1 MB.

Step 4: Fix the top of the page

Remove lazy loading from visible images and add width and height.

What success looks like: the main image loads promptly and the page does not jump.

Step 5: Work through review and advice items

Improve generic or mismatched alt text, formats, smaller versions and file names as time allows.

What success looks like: the remaining items are ones you have decided to accept.

Step 6: Recheck with a new full scan

Image Doctor shows the state at the last full scan, so it will not change until you scan again. Run a new full scan, open the Images tab and compare.

What success looks like: the findings you fixed have gone and no new ones appeared.

Final verification checklist

No image address returns an error, and none returns something other than an image.
Every meaningful image has alt text, and decorative images have alt="".
No picture the scan asked about is 1 MB or more.
Images above the fold are not lazy loaded and have width and height.
A new full scan confirms the fixes.

Common mistakes to avoid

Adding empty alt text to every image to clear the list. Informative images need real descriptions.
Expecting CSS backgrounds to appear. Image Doctor lists images in the HTML, not CSS backgrounds or images drawn by scripts.
Renaming files without updating pages. A new file name is a new address.
Forgetting to rescan. The list updates only after a new full scan.

Frequently asked questions

What is Image Doctor in Crawvix?

Image Doctor lists the images found in the HTML of your scanned pages and checks them for problems such as missing alt text, broken addresses, large files and missing dimensions. It is included in every Crawvix plan and appears in the Images tab for each verified website.

Does Image Doctor change or compress my images?

No. It only reads your website and never changes it. It does not compress or edit pictures, so you make the fixes in your CMS, editor or code.

Does Image Doctor download my pictures?

No. It asks the server for the status, content type and file size with HEAD requests, which return headers and not the picture. It never downloads or stores the images.

Why are some images missing from the list?

The list covers images written into the HTML of the pages Crawvix read, up to 2,000 unique images. CSS background images and images drawn by scripts are not listed, and pages not reached in the scan are not included.

Can I use Image Doctor on the free website sample?

No. It needs a full scan of a verified website and is not available for the free sample. See pricing.

Will fixing every finding improve my rankings?

No tool can promise that. The fixes can make pages more accessible and lighter to load, but rankings depend on many other factors.

Will Image Doctor write alt text for me?

Not yet. Suggested alt text for you to review is planned (the Alt Text Writer) but not available. For now you write the alt text yourself.

Official references

Next step: Learn more about Image Doctor and see how Crawvix checks a website. This guide gives technical information and no guarantee of rankings, traffic or indexing.