Alt tags - will they harm or help my site?

[delta4]

You need to detail a bit better so we can help. Alt tags are html code and resizing images is a different thing.

[eddiebooth]

Are you mixing up property attributes for the file rather than an alt tag?

An alt tag won't add any file size to a file, changing the attribute will change filesizes, for images file attributes I find they can be useful when uploading large amounts of images as wordpress and other cms's can automatically pick up the image file attributes.

You hit the nail on the head! Since posting I have found out that 'tags' in my image properties are not the same as 'alt tags'. So, I can get rid of these, bringing my image kb's down to a reasonable size- glad I hadnt uploaded them.
It was worth the post though, as from some of the other comments here it seems I am not the only person who confuses the two types of tags.

thanks everyone

[JJMcClure]

You hit the nail on the head! Since posting I have found out that 'tags' in my image properties are not the same as 'alt tags'. So, I can get rid of these, bringing my image kb's down to a reasonable size- glad I hadnt uploaded them.
It was worth the post though, as from some of the other comments here it seems I am not the only person who confuses the two types of tags.

As I've already pointed out in this thread, and it may help lessen the confusion to really grasp this, the Alt Description is not a Tag, it's an Attribute.

[grynge]

You hit the nail on the head! Since posting I have found out that 'tags' in my image properties are not the same as 'alt tags'. So, I can get rid of these, bringing my image kb's down to a reasonable size- glad I hadnt uploaded them.
It was worth the post though, as from some of the other comments here it seems I am not the only person who confuses the two types of tags.

thanks everyone

1 bonus of using the file property attribute is that if anyone steals your images you can instantly prove that it is your images that they are stealing.

Whether or not the search engines also read the file property attribute I don't know as I have no proof they do or don't but it surely can't hurt, google read pdf, and can read parts of swf and js and all I can wonder is because they can match images fairly well are they using internal file markers as well?

[grynge]

I can't seem to find any mention of the internal data structure of images with google (except in picasa)

But I did find this snippet

Update: Some of you have asked about the difference between the "alt" and "title" attributes. According to the W3C recommendations, the "alt" attribute specifies an alternate text for user agents that cannot display images, forms or applets. The "title" attribute is a bit different: it "offers advisory information about the element for which it is set." As the Googlebot does not see the images directly, we generally concentrate on the information provided in the "alt" attribute. Feel free to supplement the "alt" attribute with "title" and other attributes if they provide value to your users!

Followed by a comment from Dave (an official G blogger)

Google does use EXIF data in Picasa web albums.

[akirk]

The 'tags' / data being added in Irfanview / Photoshop etc. are EXIF / IPTC tags - used commonly to keyword photos for searching in software such as Bridge / Lightroom / etc.
they will add to image size as they are adding data into the image...
one of the reasons that Photoshop has a 'save to web' function is that it strips this excess data out to reduce file size...

You can read these online using things such as the EXIF library in PHP - useful for image libraries (wrote one last year) where the owner can upload the images having tagged them offline and then the website can read that / drop it in a database and use it for searches a la getty images...

totally different issue from the alt tag being described above (on that note that if you expect the alt tag to provide a tooltip when you hover over an image - it doesn't work in Firefox, you need the same info in the alt tag and the title tag)

Alasdair