The following table shows HTML tags and attributes that are known to contain URL values and their support in htmltest.

Tag / Attr	HTML	Support?	Function
a href=url	4	Yes	checkLink
area href=url	4	Yes	checkGeneric
audio src=url	5	Yes	checkGeneric
base href=url	4	Yes, relative only
blockquote cite=url	4	Yes	checkGeneric
button formaction=url	5
del cite=url	4	Yes	checkGeneric
DOCTYPE	~	Yes	checkDoctype
embed src=url	5	Yes	checkGeneric
form action=url	4
iframe src=url	4	Yes	checkGeneric
img src=url	4	Yes	checkImg
img srcset=url1 res1 url2 res2	5	Planned
img usemap=url	4	Yes	checkImg
input formaction=url	5
input src=url	4	Yes	checkGeneric
input usemap=url	4	Planned
ins cite=url	4	Yes	checkGeneric
link href=url	4	Yes	checkLink
meta http-equiv="refresh"	4	Yes	checkMeta
object data=url	4	Yes	checkGeneric
object usemap=url	4	Planned
q cite=url	4	Yes	checkGeneric
script src=url	4	Yes	checkScript
source src=url	5	Yes	checkGeneric
video poster=url	5	Yes	checkGeneric
video src=url	5	Yes	checkGeneric

The following tag/attribute combinations are known but are depreciated in HTML5 and are therefore unsupported in htmltest.

• applet archive=url
• applet codebase=url
• body background=url
• frame longdesc=url
• frame href=url
• head profile=url
• iframe longdesc=url
• img longdesc=url
• object archive=url
• object classid=url
• object codebase=url
• command icon=url
• html manifest=url