http://validator.w3.org/
1. Just type in your web page URL in the box provided next to the word "Address:".
2. Click on the "Check" button below.
3. It will show you a long list report of errors.
4. Scroll down until you see this bold line that says:required attribute "alt" not specified.
5. From here you will know specifically which image or images have no "alt" attribute.
ALT TEXT CHECKER
https://www.dur.ac.uk/cis/web/accessibility/tools/alttext/
1. Type in your webpage URL in the empty box provided.
2. Click on "Check URL" button.
WEBPAGE IMAGE SEO CHECKER TOOL
http://gh-export.us/image_seo/
1. Type your blog webpage in the box provided.
2. Click "Go!" button.
IMAGE & LINK ANALYZER
http://www.internetmarketingninjas.com/broken-links-tool/
SCREAMING FROG
http://www.screamingfrog.co.uk/seo-spider/
This one you need to download it into your computer.
1. Click open Screaming Frog,
2. Type in your webpage URL into the box next to the text: Enter url to spider:
3. Type the "Start" button.
4. Wait for a while and it will show you the result.
5. On the right hand side of the page, you can see the result for Missing Alt Text.
IMAGE ANALYSER
http://juicystudio.com/services/image.php
1. Paste your webpage URL in the box provided.
2. Click on "Test Images" button.
WAVE WEB ACCESSIBILITY EVALUATION TOOL
http://wave.webaim.org/
1. Type in your webpage or blog post URL in the box.
2. Click on the arrow icon or just press the "Enter" key.
* Some of these tools also provide other useful evaluation reports other than the alt tag.
Note: Type in webpage URL. It means your blog post URL and not your blog URL (homepage).