Google Image Search to better understand and search bots can easily crawl your images. Effect of alt text was showed in below image.
Image was not displayed to the user for some reason, but text was there.
Optimizing tips to be followed:
- File names and alt text should be brief, short and descriptive. Don't give generic file names like "img.jpg", "pic1.gif", "1.jpg. Avoid writing extremely lengthy file names and pasting entire sentences.
- Use commonly supported file types like JPEG, GIF, PNG, and BMP formats.
- Reduce your images size because images of low size can load fast. Use Image optimization tool to compress your image size without affecting image quality or use any photo-shop software.