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.