A few weeks ago Danny showed us some of the basics for video SEO, a medium that may not initially seem valuable for SEO purposes. Well, Danny dispelled that illusion swiftly, with a little help from his friend Doc Brown. This week, Danny's out there alone but still manages to show us that words aren't all they're cracked up to be; videos can yield some great SEO value, too. Besides giving us proven and actionable suggestions, Danny also postulates on some experimental and potential ways to optimize images that may prove useful now and in the future.
Video Transcription
Hello, everybody. My name is Danny Dover. I work here at SEOmoz as the lead SEO. On today's Whiteboard Friday, I'm going to tell you about the basics of image SEO. We found, when we were doing correlation analysis, that images and specifically the alt text that's inside of them are a remarkably well-correlated metric for SEO. Besides just being useful for people, images are also, it turns out, useful for search engines. I think part of the reason behind that is that pages that are well developed tend to also have images on them because it helps portray information in a way that textual based content can't do.
Let me go over some of the important factors with image SEO. Number one, I already mentioned this a little bit, is alt text. Alt text is the text that you provide for an image in case it can't be displayed. Maybe the image is gone or maybe someone is using a program that can't display images. This is the text that takes it place. So it makes a lot of sense from an SEO perspective that this metric is going to be important because it's the information you tell the search engines and other technologies what the image represents. With these, I recommend keeping them below about 140 characters. It's a rough rule of thumb. Also, have them be descriptive and in line with what you're trying to target for that page.
Number two is the file name. This works off the exact same principles. The file name is also information you give directly to the search engines and to other technologies to identify what the information is about. I would gander, if you will, that the file name is probably a rougher signal than the alt text. Alt text, from my experience, when it's there, which is not all the time, in fact, alt text is not included many times which is bad for SEO. But when it is included, it tends to be a clearer signal than a file name which a lot of times is just algorithmically generated by the timestamp, so it's just a bunch of numbers.
Number three is the surrounding text. I think a lot of people don't think about this when they're thinking about image SEO. The text around an image tells a lot about the image itself. This makes sense, right? You'll see a lot of times where images will be on a blog post and you'll have a caption describing the image. This is just another signal telling the search engine and other people and technologies what it is this image is about. The surrounding text, and that can either be a caption, like you've seen traditionally, or it can just be the paragraphs around the image. A lot of times an image will be used to supplement what the textual information is talking about. So the surrounding text is very important.
Fourth, as with all SEO, inbound links are important. It wouldn't necessarily be inbound links to the image URL, although it could be, but what I mean in this context is links going to the page that has the image embedded on it. Just like in normal SEO, the anchor text of those inbound links and where they're coming from and how many of them are all really important factors for image SEO and then SEO in general.
Last is number five which is human categorization. The search engines, especially at the beginning when they were developing this image recognition software, used humans. They would hire people and they'd say, "Label this." Google was semi-famous for creating this game, Google Image Labeler, which I think you can still find online, where it would show you an image of, say, an apple. They would ask you in Family Feud style, which is a game show here in the States, to list words that are associated with that object. You'd say something like apple, and you'd earn points if someone else also said apple. Maybe it's red, Fuji, or Grandma Smith, or whatever it is. So other words that are associated with the image. And that way they could train their software to start to understand what general shapes and ideas mean within images.
On the other side here, I have some more theoretical things that search engines may be using, while the things on this side are the things that we know they're using. We've heard search engineers talk about this. We've seen direct evidence. These are things that I think you should pay attention to but probably just going forward. It's more just for your knowledge rather than for you to use on your day to day.
The first one is OCR. OCR stands for optical character recognition. It's a very established software. It comes in a lot of Adobe products. You can get it in lots of places. What it does is it scans an image and can identify characters in it, characters like letters or numbers or spaces or whatever. From that, you can take actual text out of images. Again, this is a very popular software. It seems very likely to me that search engines are using this at least to some degree. It would be very costly for them from a resource perspective to use on every image on the Internet, but it would certainly make sense if they were using it on some or at least playing around with the technology.
Number two is color analysis. It's very easy from a development perspective to identify at least one color, maybe the primary color, within an image. You pick a pixel and you see what the hex code or whatever it is that you're measuring that on, it will be based on file type. It's pretty easy to get a general idea of what the color of an image is. This is helpful from a design standpoint if you're looking for certain color themes that go with each other or color patterns. Now we've seen this actually in the SERPs, so if you go to Google image search, you can see now, and Bing actually had this first, you can go to the image SERPs and you can actually pick to see only images that are of a certain color. Black and white is the obvious one, but then other colors as well.
Number three is file size and type. This one, I think, is more all about the extreme. If the image is ridiculously big, it's probably not going to get indexed just because the search engines don't want to spend the resources on that. The exception to that would be if it's ridiculously well linked to also. It's about finding these outliers. You probably don't want to have an image that's really, really big. It's probably not going to get indexed. Again, I think what it really comes down to is this is hurtful for users also because they're going to have to spend time downloading that. If bandwidth is a concern, they're probably going to click away to begin with. Image size and along with image type, the standard image things are all probably fine for Google.
I've heard just a rough rumor here that JPEG is preferred, but honestly GIFs and PNGs and all those other things are probably fine. I would not worry about those aspects. Only worry about it if you're using obscure file formats, which you shouldn't be doing to begin with.
The last one on here is the other images on the page. This is twofold. The first part being the other images on the page are likely related to the given image and that's because they're on the same page. Right? The other part, and I see this happen a lot especially with bigger clients, is when you put lots and lots of images on one page, like an image gallery, those pages tend to be very hard to get indexed. The reason for that is there's not a lot unique textual content. A lot of times it's just overwhelming to users. It doesn't provide a lot of benefit in a search result.
That's all the time I got today. I appreciate you listening to this. Please feel free to ask questions in the comments below. Thank you.
Video transcription by SpeechPad.com
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"I've heard just a rough rumor here that JPEG is preferred, but honestly GIFs and PNGs and all those other things are probably fine. I would not worry about those aspects. Only worry about it if you're using obscure file formats, which you shouldn't be doing to begin with."
Danny you should worry about such aspects. This is because size of a PNG file is about 20% smaller than the same size GIF file. Also unlike GIF, PNG file can be saved up to 24 bits which means you get more color depth. Since JPEG uses a lossy compression (image loses quality and information each time it is saved) its filesize is almost always smaller than a PNG. Google recommends using JPEG wherever you can. So those are not rumours.
[Here are the file sizes of same graphic in various formats:
* JPG, 60 quality - 32K <<--- Note the size
* PNG-8, 256 colors - 37K
* GIF, 256 colors - 42K
* PNG-24 - 146K <<-- Note the size
"For very detailed and colorful artwork or for photographics, JPG and 24-bit PNG are typically used because they have a much larger color palette. While a 24-bit PNG results in superior image quality, this comes at the price of a larger file size. When you can, use JPG instead and adjust the quality setting so you can compress the image as much as possible within your desired tolerance for image quality."
Source: https://code.google.com/speed/articles/optimizing-images.html]
Since site speed is now a ranking factor, you better speed up your images :)
I think you are mixing two aspects:
I don't think Google will prefer ranking JPGs better than PNGs only because it's a JPG. It could prefer JPG because it's smaller in that particular case. Regarding 1) there should be no difference between JPGs and PNGs, regarding 2) either of the two could be the better option - that one, which is smaller and therefore has a decreased loading time.
Generally preferring a single format is imho the wrong way, since it depends on the type of the image (photo, drawing, transparency etc.). Perhaps this changes when Google releases (or wants to push) its own image format...
Optimizing speed is not an indirect seo aspect as site speed is now officialy a Ranking Factor and file size of images has major impact on download time. So i am not mixing anything here. Google doesn't want to rank high an image which takes forever to download, so images which load faster should be getting some sort of preference in addition to other ranking signals. I never said that you should always use the same image format. For photographic images i find JPEG as best and for all other PNG. I don't see any reason to use GIF other than for animation.
I understand your point and you are of course right. The only difference I wanted to emphasize, that it doesn't matter which file format you are using (as long you stick to the common ones), what matters is the file size (which is an effect of the file format and content).
Besides of that, optimising file size should be done all the time, regardless of seo :-)
The file format does matter, but from a design and quality perspective, not an SEO one. All JPGs work well as PNGs, but not all PNGs work well as JPGs for example.
I will be interested to see when Google releases their own image format whether that will be higher-ranked and/or more readily indexed than other formats. My suspicion is that they will claim the speed benefits are the key enhancing factor for SEO.
- Jenni
Awesome discussion, guys! Very helpful, both from an SEO, and a Design, perspective.
Hi Seo-Himanshu,
Do you mean that the max. size of a .jpg should be 32K?
Danny, I did no hear anything about geotagging the image? How much does this come into play?
I think what is Danny also missing is the use of metadata in images, such as EXIF etc. (incl. Geodata). Is there a positive effect and what fields are used?
I've also heard that overoptimizing image alt-text can hurt you. Do you recommend using alt-text in every single image on the page? Should that language in the alt-text be SEO friendly or purely descriptive?
The SEO Moz home page is an interesting example. Can you explain why having the Alt Text "Loved by Zillow.com, Disney, overstock.com and more!" is better than having no alt text whatsoever? Why not use...."Our SEO tools are loved by companies such as Zillow.com and Disney."
In general, we struggle with the best practices for the following.....
Buttons
Logos/Credibility Icons
Arrows and other graphical elements
The alt attribut has to be on every single image on the page, since it is a mandatory element in html.
Logos and all other structuring images should be packed in a CSS sprite - also for improving page speed (reducing http requests).
I do like using the Logo for the alt tag so as not to worry about the Home butting not being keyword sensitive. All others should be in s sprite.
>The alt attribut has to be on every single image on the page, since it is a mandatory element in html.
The attribute may have no content though. If an image has no visual content (is used for aesthetic purposes only) then IMO it shouldn't have any alt text just a blank, alt="", to indicate it hasn't been forgotten (and to remain standards compliant).
For buttons, the alt text acts as the anchor text of the link, so it should be optimized for the target page, not the page the button is on.
As far as I could see, some people were not using pictures because they were afraid they do not count for SEO purposes. But if one uses the same keywords in the alt text, title and description, isn't it a bit spammy too?
I think that Facebook can recognize faces in images. I would assume that Google should have no problems to recognize text in images. Not sure if the text in images is indexed.
Is it still true that HTML is much better than text in image? Has scanning of images by search engines improved?
I remember watching a Matt Cutts video a while ago where he was talking about images and said that Google had considered doing OCR on images but at the done had not done it
yes i agree with yr point
The 'face recognition' in Facebook is still a manual process, where users can tag images by clicking on an area and entering a name.
I`m still not sure whether text in an image is recognised by Google properly yet or if HTML is still the best option. I think having the text in an image is potentially still not as effective.
Agreed.
Even dedicated font-identifying services such as What The Font still have room for improvement in trying to intepret characters.
This is a good starter point for people. Although not necessarily "basic", image sitemaps are massively important. After proper implementation of these on one of my image database type site, I saw an increase of several thousand visits per month with no other changes of note on the site. These results were from the blended/universal search and not specific image searches (which are only a tiny percentage of the visits accrued.)
What are the best / easiest ways to generate an image sitemap?
Now speed has become a factor in SEO, I am using the W3 Total Cache plugin for most of my WordPress-powered sites. This plugin gives the option to use a CDN for serving images. I am a bit hesitant about using this because I am afraid that having my images on another domain will be bad for image SEO. Is this correct? Does the use of a CDN for serving images negatively effect the ranking in image search?
Hi Danny, I think you've forgotten the use of the title-attribute, which is also a very important source of content for search engines. I personally would put it left as second list item :-)
Stephan
Image title tag comes on my mind, too. And how's image title related to ALT? When I use title for image, I tend to make it similar to ALT but not exactly the same. Although, I didn't measure the results of that technique.
When searching for an alt/title text, I try to remember the original semantics of the attributes:
alt = what should be displayed, when the image is not present (description of the image)
title = what is the title of the image
Because the title is often (but not necessarily) somehow a description of the image, both texts share a certain degree of similarity - but I try to use the small semantic difference as a guide.
Title tag is not the same thing as title attribute.
Title attribute doesn't have any impact on SEO. It's can be valuable information for user.
Can you point some research that will support "Title attribute doesn't have any impact on SEO." thesis?
I know mayority of SEOers claim that but there are SEOers claim it have an impact, too.
ps
Pozdrav za Crnu Goru :)
Sorry, no research I can offer you. But I'll try to give you an answer.
To use the title attribute is a good practice in order to follow the W3C standards. The W3C standard aims to offer a code clean website. A code clean website can make life easier to bots, therefore let them scan better a page, which results in better indexing and better indexing always helps.
Is it by itself an inportant factor? Doesn't seems so.
@Acca
There is huge misss-understanding about terms of "Titile tag" and "title attribute". Look here in comments, so many proffesionals but still you can find wrong terms. Personally i don't like title attribute, it just distract user attention... I can't rememmber when i hovered some image to see the title.
BTW you saw studies about title tag, not attribute ;).
I have found using hyphens instead of under scores in the image name seems to work better. Has any one else experienced anything similar?
I would like to store my images online and get some SEO value from Google image search. I am a bit unsure about using Flickr because of the nofollow, is there a better alternative out there for SEO juice?
Is there a more recent article on this - I trust a lot has changed since. I was especially looking for some info on what part unique images have a say in SEO. Thanks.
I couldn't agree more that the 'face recognition' in Facebook is still a manual process, where users can tag images by clicking on an area and entering a name.
Image Optimization is important Thinga in seo.This tips are very helpful for me.Thanks for sharing.
Image SEO is something that's always confused me a bit. There seem to be some real red herrings in the mix when you look at the results in Google Images.
Thanks for the tips :-)
These tips were extremely helpful. Optimizing your images are extremely important. Thank you.
I know this is an old post, but I have a doubt about image SEO. On the first place I know we need to try to optimize everything we can... that said. optimizing the name of an image, should be done how? For my example we are optimizing car rental images and right now we have an image that's called "8.jpg" and it has alt attributes like "familiy car rental in cancun standar version" or so and it also has a title text with about the same optimization. About the name of the image we are going to change it, and the question here is, How optimized should it be? Let's say we have a Dodge Charger for rent, should I name my image "dodge-charger.jpg"? or "car-rental-dodge-charger.jpg?
The site in question is www.america-carrental.com
Hi Noel!
This is a perfect question for our Q&A forum, actually. :) It's not likely to get many views in here.
I know, but I'm not ready to invest $99 USD :S
Thank you very much for this very important information, But the problem that we face is always that: First: What are the sites that accept image such as backLink Secondly, most of the sites and forums, especially those that contain high PageRank does not accept anchor text Finally: Is there a body or a particular text to put the URL of the image + text of its own, for example, we all know this formula: If we had (How to lose weight), and we want to put them in the form of anchor text put it thus: <a href = "https://www.youtube.com/watch?v=linkhere"> how to lose weight, </a> So how to be the formula for a photo What is the solution? Thank you again
[link removed]
Fantastic Video! Thanks for the advice.
Awesome I love it thanks for the tips!
I have read your blog and found this is very useful for us. Thanks for sharing important information with us.
Thanks, well presented and good info. I have two quick questions regarding Wordpress and Image SEO.
1. By default wordpress includes an image title tag, any idea if there is any benefit in having this in addition to the alt tag?
2. By default wordpress stores images in folders several levels deep, often something like URL.com/wp-content/uploads/year/month/filename - any idea on whether there is any benefit/preference by the search engines in having images in a folder closer to the root (shorter url structure)? i.e URL.com/images
Thanks.
Hrmm, I guess posting a question 3 days after the post was published and hoping for an answer was expecting too much...
What about the very small images? How does these affect the SEO?
In terms of Google images I am still left wondering what influences the one row of "sample" images on the first page of Google search results. For some searche terms you see a sampling on the first page, for other searche terms you must search Google Images to see any at all. Any idea what determines this?
Okay, no one is asking the important question: who/what is that little man drawing underneath "other images on page" on the whiteboard?
This is gonna bug me until i get an answer... help me out mozzers!
Any ideas on how background css images are treated?
Haven't found an evidence, but I would assume, that they are not indexed, cause they are there only for layout-purposes. That's why they are CSS-Images. Furthermore indexing such things as multiple images in a css sprite would not be sensible.
We all know that inbound links are important for SEO. But, in case of images, do they work? Have you tried and tested them? I am saying so because I haven't seen inbound links working for me after getting a substantial amount of links done for the image URL as well as the page URL.
Infographics are not images? Therefore in their case that works, a lot.
To confirm Google's ability to OCR images. In Google docs there is an option to upload a file from your PC. After selecting the file there is a check box with the following question "Convert text from PDF or image files to Google Docs documents" . Well if they do it in Google Docs I'm sure they are/will do it for Google images too.
https://docs.google.com/support/bin/answer.py?answer=176692&hl=en
Looks like the player you are using for the whiteboard fridays hides the full screen button. Should be an easy fix to just expand the width of the videos
What are you suppose to do with # 5 Human Categorization?
use it :)
if your image is an apple, your alt text might be 'apple' as well, but if the text surrounding the images only has 'red' and 'fruity' then google might still point those words towards your keyword without using the actual word 'apple', because of the categories
Is there any correlation between higher number of images and number of links to a page? I would think that having good images on your page would make it more attractive for links and sharing than a page with only text. Flickr creative commons and iStock photo are my favorite sources for good photos.
Thanks for the basics.
Is the "longdesc" attributes ( and the related text file ) are useful for the SEO ?
right on..I am actually meeting with our design and product team today to push for a more SEO friendly images...We have a huge eCommerce website but our image naming conventions are very poor. This video would be a good back up.
Also a while back, from one of Matt Cutts videos, he did mention image size was important so I do believe Google maybe doing some OCR specially on blog posts on smaller images. So yes file size is big.
In addition to OCR and color recognition, Bing also has the ability to identify faces and shoulders. In their image search there are options for "Just faces" and "Head & shoulders." I wouldn't be surprised if Google also has this capability, and if they don't then I'm certain they're working on it.
Additionally, it seems to be a good idea to keep as much graphical content as you can in CSS sprites, so as not to dilute the importance of actual in-content images.
In some of the literature accompanying their new image search, Google claimed they can identify species of leopard by the pattern of their spots. It's virtually certain that they would do face and figure recognition before something like that.
https://googleblog.blogspot.com/2010/07/ooh-ahh-google-images-presents-nicer.html
Aaron, i have five pictures in top 10 search for "seo optimization" on my language from over 2 310 000 results and i have one more usefull advance for your guide: Use long tail keywords! For Google alt of image like: "seo" or "clothes", "money" and other in this way is only one: Spam.
Pictures with this type of alt attribute have no chance to rank for high traffic keywords. My experiments show that should be used more than two words. Best result is with three and four keywords in alt :)