One SEO pro had a question on images. They wanted to know about the importance of image file names for site ranking and images in web search in general.
They are using an intelligent CDN (content delivery network) provider, which has been replacing the image file names with unique numbers.
And they noticed that all the images are 404s in Search Console.
Disabling the CDN would significantly degrade overall site performance. So their question is: will image alt text and caption be sufficient for Google to understand, without an appropriate image, file name, and title?
John explained that there are two things he recommends looking at. The first is, if these are images that you need to have indexed in image search, then you should definitely make sure that you have a stable file name for your images.
That’s the most important element here.
Also, John pointed out that the SEO professional doesn’t mention that the numbers or URLs change. Sometimes the CDN essentially provides a session-based ID for each image.
And if the image URL changes every time Google crawls, then they will never be able to index these images properly.
This is mostly because for images, Google tends to be a bit slower regarding crawling and indexing. So if they see an image once, they say “Oh, we should take a look at this,” and then they try and crawl it again, then at some later stage the number has changed by then.
Then they will just drop that image from their search results from the image rankings. And they will just say “Oh: this image that we thought was there is really no longer here.”
John then explained that the most important part of figuring this out is: do you care about image search?
If so, you need to make sure that you have a stable URL for all of these images. It doesn’t matter if it’s a number, or if it’s text, or anything like that.
Just that the URL to the image is a stable URL. That’s the most important part here.
The other part that the SEO pro mentioned is the image alt text and captions, which suggests that they actually are interested in web search, and not necessarily image search.
For web search, Google doesn’t need to be able to crawl and index the images.
Because Google search just looks at the web pages themselves. Things like alt text, any captions, headings on the page–all play into understanding the page a bit better.
And for web search, that’s all Google needs. If all the images were, for example, 404ed all the time or blocked by robots.txt for web search, we would still treat that page exactly the same as if we were able to index all of these images.
This happens at approximately the 24:56 mark in the video.
John Mueller Hangout Transcript
John (Submitted Question) 24:56
So the first question I have here is about images. We have a question about the importance of image file names for site ranking. We’re using an intelligent CDN provider, which has been replacing the image file names with unique numbers.
And noticed that all the images are 404s in Search Console. Disabling the CDN would significantly degrade overall site performance. Will image alt texts and captions be sufficient for Google to understand without an appropriate image, file name and title.
John (Answer) 25:29
So I think there are two things here that I would look at. On the one hand, if these are images that you need to have indexed in image search, then you should definitely make sure that you have a stable file name for your images.
That’s, I think, kind of the most important element here. You don’t mention that these numbers or these URLs change. But sometimes the CDN essentially provides a kind of a session based ID for each image. And if the image URL changes, every time we crawl, then essentially, we’ll never be able to index those images properly.
This is mostly because for images, we tend to be a little bit slower with regards to crawling and indexing. So if we kind of see an image once, and we say, oh, we should take a look at this, and we try to crawl it again, at some later stage and the number has changed by then. Then we will just drop that image from our search results from the image rankings.
And essentially, we will say, Oh, well, this image that we thought was here is actually no longer here. And so the most important part here is kind of figuring out, do you care about image search? And if so, you need to make sure that you have a stable URL for all of these images.
It doesn’t matter if it’s a number, or if it’s a text or anything like that, it should just be stable. That’s kind of the most important part here. The other part that you mentioned is the image alt texts and the captions, which kind of suggests that you actually are interested in web search, not necessarily image search.
And for web search, we don’t need to be able to crawl and index the images. Because we essentially just look at the web pages themselves. So things like the alt text, any captions, headings on the page–all of that play into understanding this page a little bit better. And for web search, that’s all we need.
If all of the images were, for example, 404 all the time or blocked by robots.txt for web search, we would still treat that page exactly the same as if we were able to index all of those images.
It’s just in image search itself, that’s where we need to be able to kind of index these images and understand that they’re stable URLs and understand how they kind of connect with the rest of your site.
