AltTextify.net browser extension for Google Chrome, Mozilla Firefox and Microsoft Edge lets you right-click on any image on a page and generate alt text. You can then copy and paste the alt text anywhere you need it.
When browsing a webpage with images, simply right-click on any image and select “AltTextify: Generate Alt Text” from the context menu.
A small window will then appear in the top-right corner of your screen displaying the generated alt text. You can then copy the alt text to the clipboard by clicking the Copy button.