The following characters cannot be used as part of the parameter values in a Composer button URL. Using any of these characters will cause your solution to fail.

Character NameCharacter
Colon:
Hash#
Open Parenthesis(
Close Parenthesis)
Double Quotes"
Percentage%
Backslash\

URL Encoding Illegal Characters

The above illegal characters can be encoded using URL Encoding. This will allow you to use them in your parameter values in your Composer URL. Below are their encoded values:

Character NameCharacterEncoded Value
Colon:%3A
Hash#%23
Open Parenthesis(%28
Close Parenthesis)%29
Double Quotes"%22
Percentage%%25
Backslash\%5C

Using the SUBSTITUTE Function in Salesforce

If you are referencing a Salesforce field as a parameter value in your Composer URL, and this field may contain ampersands, you can create a Salesforce formula field and use the SUBSTITUTE Function to replace Ampersands within the field value. You would then use the formula field in the parameter instead. See this article for details: Replace Ampersands in Reference Field Data