Alt attributes
Suchmaschinen können Bildinhalte nur ungenau einlesen. Die Bildinhalte werden also durch den Alt-Tag/ Alt Attribute beschrieben. Deshalb empfehlen wir, Fotos und Grafiken immer mit Alt Attributen zu kennzeichnen. Denn erst durch textbasierte Inhaltsangaben – Alt Attribute – erschließen sich Suchmaschinen das Dargestellte. Das wird wiederum durch besseres Ranking belohnt. Zudem nutzen immer mehr Leser die Google Bildersuche z. B. für den Onlinekauf von Produkten. Optimierung von Bilddateien lohnt sich für die Suchmaschinenoptimierung auf jeden Fall.
The word alt attribute is composed of "alternate" and attribute for property. Synonyms such as "alt tag" are also common. In this case, the "tag" refers to the markup in the HTML code.
Attention! There is a risk of confusion here: The Alt attribute is not a title tag for images. Because the latter plays its own role in SEO image optimization. By the way, the title tag is shown in the mouse over. This information is shown when you move the cursor over the image file. But: If the Title Tag is not filled in, the Alt-tag appears.
Why is the Alt attribute used?
The most important advantage of Alt tags is that Google and other search engines transfer the image content into text-based content. The second advantage is that if image files cannot be displayed in Google Image Search, the Alt attribute appears instead. Thus, the reader cannot see the image, but can read image content. It is often forgotten that alt attributes play an important role in accessibility. Speech assistants (screen readers) read the image content (Alt attribute) aloud. This gives people who are affected by vision loss, for example, an impression of what image content is stored. Alt attributes also have an important function for voice search.
What technical hurdles can Alt Attributes bridge?
The content stored in the Alt attributes is always displayed as text when image display is not possible. This is the case, for example, when user agents do not support images, the browser does not automatically load graphics and photos. Server problems can also hinder image rendering. Problems in image rendering often occur when image folders on the server have been moved and search engines cannot reach the image URL. In these cases, the Alt attribute is shown instead of the graphic or photo.
Do alt attributes have an effect on SEO?
Definitely yes! Google & Co are working flat out on image recognition software. However, the capture of image content is not yet one hundred percent successful. At the same time, more and more users are using image search for online shopping.
In order to ensure that images are correctly classified, e.g. in Google Image, the displayed content must be described in text-based form. In this way, website operators ensure that crawlers get the information they need and render the relevant image content to users - through Alt Attributes.
The Alt attribute is stored in the source code as an HTML element directly in the image link and could look like this, for example:
On the SEO side es there are no rules how long or short an Alt attribute should be. As a rule of thumb gives: As short and concise as possible and preferably using keywords. Keyword stuffing must be avoided. Alt attributes should really reflect what is being presented and not rely solely on keyword usage. Es is about improving the reader's user experience. So if someone searches Google Image "blue knitted sweater", they want exactly this result - not image files with green sweaters that only want to appeal to high search volumes.
Alt attributes should be left blank only in exceptional cases. Every image file (graphic, photo, etc.) should be alt-tagged. Empty alt tags confuse crawlers and screen readers. An empty alt attribute is wasted effort and looks like this alt="". In short: High-quality, lovingly created graphic files cannot be classified here - and do not find any attention in Google Image Search. Users therefore fall back on another offer.
This has SEO relevance for alt attributes:
- precise and concise description of the image content (best practice: 2 - 3 words)
- Use of keywords where possible
- Image URLs keyword optimized (if possible), avoid digits, no capital letters/ special characters/ underscores