What is the size limit of a Base64 DataURL image?

Citing MDN on this:

Length limitations

Although Mozilla supports data URIs of essentially unlimited length, browsers are not required to support any particular maximum length of data. For example, the Opera 11 browser limits data URIs to around 65000 characters.

And caniuse.com, where you can also look up the support across browsers:

Support in Internet Explorer 8 is limited to images and linked resources like CSS files, not HTML files. Max URI length in IE8 is 32KB. In IE9 JavaScript files are supported too and the maximum size limit set to 4GB.

Not all browsers support the data URI scheme. IE7 and earlier doesn't support data uri's at all. IE8 has a 32k limit.

http://www.bennadel.com/blog/2002-Creating-Base64-Encoded-Data-URLs-For-Images-In-ColdFusion.htm