What are the valid characters and length of a Sub-ID?

Sub-ID values can be up to 50 characters and may contain letters, numbers, and the following characters:
 
   - hyphen @ at symbol
  _ underscore + plus sign
  . period : colon
  = equals sign { opening brace
  ? question mark } closing brace
  % percent sign    

The Sub-ID characters only apply when passing data to your tracking links and rotators as Sub-IDs:

http://$linkdomain/dietplan/subid1/subid2/…

The restrictions don’t apply when you’re adding ad network or other tokens (such as #S1#) to your ClickMagick link because those tokens will be replaced with valid characters by the ad network before the link is used.

 
Caution: if you use a Sub-ID that looks like a cost-per-click value, such as /0.63, ClickMagick will interpret that as a cost value if it is at the very end of the URL. See:
 
  Can I pass in a cost value with each click?

Also, Sub-IDs that contain only 5 or 6-digit numbers such as /360138 are considered special as well and will be interpreted as numerical link or rotator IDs rather than Sub-IDs. That means that If you try to pass a date like “December 12, 2017” as /121217, you will run into trouble...

ClickMagick’s click IDs—which are 9 digits or more—will be passed as Sub-IDs just fine.