Case 3: Add query parameters to URL

Let's say there is a website called example.com that shows a mobile layout by default, but you prefer their desktop layout. Fortunately, the website supports a layout query parameter to specify which layout the website displays. Let's create a rule that adds layout=desktop automatically.

Perhaps you think you could define it as follows:

• Redirect From: https://example.com/.* (Regular Expression)
• Redirect To: $0?layout=desktop

$0 references the target URL. If you try to access example.com/hello, you're redirected to example.com/hello?layout=desktop. This feature is called substitution.

tip

Substitution is also available for the Wildcard mode since it's internally converted to Regular Expression.

However, there are a few problems with these settings.

Problem 1: Infinite loop

The current setting creates an infinite redirect loop since https://example.com/.* also targets https://example.com/hello?layout=desktop.

In this case, you can specify an excluded URL pattern that allows you to access without redirection, like this with Regular Expression:

.*[&?]layout=[^&]*.*

• .*: Matches anything
• [&?]: Matches either & or ?
• [^&]*: Matches anything except &

Problem 2: Can't handle existing parameters properly

If the target URL already has other query parameters like example.com/hello?theme=dark, the destination will be example.com/hello?theme=dark?layout=desktop (There are two ? in the URL) but you can only join the parameters with &. ? as a special character is only allowed at the beginning of the parameters. So it's not treated as a valid parameter.

In this case, change the settings like this:

• Redirect From: (https://example.com/[^?]*)(\?(.*))?
• Redirect To: $1?layout=desktop&$3

Let's take a look step by step.

• (https://example.com/[^?]*): Matches the part until the previous character of ?.
  • [^?]* matches anything except ?.
  • This is wrapped with () so you can reference it with $1 later.
• (\?(.*))?: Matches a string start with ?, which means query parameters.
  • This also matches empty string by the ? quantifier at the end of the pattern, which matches zero or one time.
  • The outer () and the inner () can be referenced with $2 and $3 later.

RegExr may help you understand the details.

note

RegExr shows an error when you don't escape / with \. Although you can escape it, it's not required since Redirect Web uses a different engine by Apple that doesn't require escaping.

This is not a perfect solution, as it redirects example.com/hello to example.com/hello?layout=desktop&, which includes an unnecessary & at the end of the URL. It's not a big deal in general, but if you wish to remove it, you can use Capturing Group Processing.

In conclusion, this is the final output:

• Redirect From: (https://example.com/[^?]*)((\?(.*))?) (Regular Expression)
• Redirect To: $1?layout=desktop$3
• Excluded URL Pattern: .*[&?]layout=[^&]*.* (Regular Expression)
• Capturing Group Processing:
  • Group: $3
  • Process: Replace Occurrences
    • Target: \?(.*)
    • Replacement: &$1

⬇️ Download the Rule

This is merely an example. You can also create multiple rules to handle each problem. It can be much simpler.