Alt tags helps the search engines understand your image/s is all about and guide them to serve your image/s to the right audience or users.

[DELETED]

The alt tag is used by screen readers, the browsers used by blind and visually impaired people, to tell them what is on the image.
Each image should have an alt text. Not just for SEO purposes but also because blind and visually impaired people otherwise won't know what the image is for.

[DELETED]

In simple words, anything that improves your user experience will help to improve your SEO status (directly or indirectly). Optimisation of alt tags for sure improves your user experience as well as indexing of your images in Google database.

Anyway how an alt text is visualized, or how does it appears.

The best practice is to include alt tags that offer a good description of the image.
All SEO is important but how much any one thing will affect your rankings is almost impossible to say. Your ranking depend on the accumulation of tons of different factors. Any one factor may have a massive or minor, or no effect.

Completely made up scenario....

You add descriptive alt tags to your images.
Google displays one of your images in a first page search result
That drives more traffic
That increases the ranking from top of page 2 to bottom of page one
That increases the traffic again.
A searcher now finds your site and decides to link to it
That backlink increases your ranking.... etc ... etc..

An alt tag, also known as "alt attribute" and "alt description," is an HTML attribute applied to image tags to provide a text alternative for search engines. Applying images to alt tags such as product photos can positively impact an ecommerce store's Search engine ranking.

Thanks so much for your replies everyone, very helpful

It is very important for SEO. Because 'ALT image Tag' increase readability score which is very important for any page content .If you don't use alt tag on your then google will consider the image as a HTML code. Which can decrease your readability score and your site can be fall in below rank.

The alt attribute provides alternative information for an image if a user for some reason cannot view it (because of slow connection, an error in the src attribute, or if the user uses a screen reader).
Without alt text, an image will be displayed as an empty icon: In Internet Explorer, Alt text also pops up when you hover over an image. Plus, Google officially confirmed it mainly focuses on alt text when trying to understand what an image is about. Alt tags provide better image context/descriptions to search engine crawlers, helping them to index an image properly.This means that alt text is valuable for SEO, in addition to being useful for users.

[DELETED]

The main purpose of alt tags is to let the crawlers read what the image is all about and it is an important ranking factor when your site consists of lot of images. In case you own an e-commerce website, including alt tags in your images will help your product to be visible in in SERPs whenever a search for similar product is performed by users.

Search engines cant read images so they read alt tags to know what your picture is about which will be later on considered in your ranking process. So it's important to add alt tags in all of your pictures because if this field is empty, it's hurting your ranking.

Hi wildescapes,

Img alt tags are very important. Google does not read images. It only reads the text, hence, alt tags are necessary.
If you have a WordPress or some other blogging/website based website, it will be easy for you. You just have to go to the library and fill the alt tags box. Else, you would have to edit the coding of your website to add the tags.

Regards

Search engines cann't read images used in your website or blogs. When we use ALT Tags for image, search engines find ALT Text in place of image. So ALT Tags are really important for optimizing images in website or blogs.

[DELETED]

If your images have alt tag with a specific keyword. Then when user search for that keyword in images, your images will have a chance to get rank on top of SERPs.

Alt Tag is basically understood your images which are used in articles and blogs. Google also checked your image status before and after indexing your website. So Alt tags are much important in SEO.

Alt tag is very important because the search engines and blind and visually impaired people can easily help to understand that for what the image is for.

Alt tag simply means an alternative, sometimes web pages take to long to load (many possible reasons for this) and the images are not visible instantly due to the slow loading speed, so it would be better to use the alt attribute to tell your users about the images if the image is not loading yet.
Similarly, SE spiders understand only the text and can't read the images or videos so it would be better to use the alt attribute to make SE spiders aware about that image and understand about the image for the better results.

It is very important for seo

A good alt tag could allow google to tell what the image is, and use it in image search results that could lead searchers to your website.

It is very important for SEO. Alt tag helps search engine to understand what is image belong to.

if you didn't heard yet about microstock business, make a couple of searches. it might apply to you also

The use can be that, if you have pages that might rank higher and can bring you profit, then we must use alt tags so that your page can up higher.
Each image should have an alt text. The purpose for SEO is because of blind and visually impaired people does not have knowledge about what the image is for.

Alt text is used within an HTML code to describe the appearance and function of an image on a page.
It is provide better image context/descriptions to search engine crawlers, helping them to index an image properly.

Hi wildescapes,

It is important to have alt tags in your images as Google is a bot which read the text written rather than seeing the image.
Een if your images are ranking well, it is always advisable to put alt tags for further optimisation.

While putting the image, just add an alt text to the image describing the image using the keywords, if they can be applied.

Regards

I think alt image tags are most important for SEO because you can get rank if you properly use alt image tags and search engine count it.

Thanks so much for your replies.
What if most of my photos are in galleries? Are alt image tags still useful here? They wont show up unless someone clicks on an image and scrolls through

[DELETED]