Do SVG docs support custom data- attributes?

Question

In HTML5, elements can have arbitrary metadata stored in XML attributes whose names start with data- such as <p data-myid="123456">. Is this part of the SVG spec too?

In practice this technique works fine for SVG docs in many places. But I'd like to know if it's part of the official SVG spec or not, because the format is young enough that there's still a lot of incompatibility between browsers, especially in mobile. So before committing to code I'd like know if I can expect future browsers to converge on supporting this.

I found this message from the working group mailing list saying they "expect [they] will" support it. Did this become official?

Answer 1

While other answers are technically correct, they omit the fact that SVG provides an alternative mechanism for data-*. SVG allows any attribute and tag to be included, as long as it doesn't conflict with existing ones (in other words: you should use namespaces).

To use this (equivalent) mechanism:

• use mydata:id instead of data-myid, like this: <p mydata:id="123456">
• make sure you define the namespace in SVG opening tag, like this: <svg xmlns:mydata="http://www.myexample.com/whatever">

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EDIT: SVG2, currently W3C Candidate Recommendation (04 October 2018), will support data- directly (without namespaces, the same as HTML). It will take some time before the support is widespread though. Thanks @cvrebert for pointing this out.