Body Rewrite iOS 5.10.0+ Mac 5.6.0+

Surge can rewrite the body of an HTTP request or response, replacing the original content with regular expressions or manipulating a JSON body with jq expressions.

Example:

[Body Rewrite]
http-request ^http(s)?://example\.com value abc
http-response ^http(s)?://example\.com documents Surge

Syntax

Each line contains a rewrite rule, with parameters separated by spaces, starting with http-request or http-response. The second parameter is the regular expression for the URL to take effect. The third parameter is the regular expression for replacement, and the fourth parameter is the content of replacement.

http-response ^https?://example\.com/ regex replacement

You may continue adding regular expressions and replacement content afterwards for consecutive replacements:

http-response ^https?://example\.com/ regex1 replacement1 regex2 replacement2
http-response ^https?://example\.com/ regex1 replacement1 regex2 replacement2 regex3 replacement3
…

The replacement supports capture group references such as $1. The ^ and $ anchors match at the beginning and end of each line of the body.

The body must be valid UTF-8 text for regex-based rewriting. If it is not, the rule is skipped and a note is added to the request journal.

JQ Body Rewrite iOS 5.14.0+ Mac 5.9.0+

You can use jq expressions to manipulate a JSON body:

http-request-jq url-pattern jq-expression
http-response-jq url-pattern jq-expression

For example:

http-response-jq ^http://httpbingo.org/anything '.headers |= with_entries(select(.key | test("^X-") | not))'

Notes:

• The body must be valid JSON; otherwise, the rule is skipped and a note is added to the request journal.
• If the jq expression produces empty output, the original body is kept.
• An invalid jq expression produces a warning and the rule is skipped.

Interaction with scripts

If both a body rewrite rule and an HTTP script match the same request or response, the body rewrite is applied first, and the script receives the rewritten body.

Limitations

• Body rewrite requires buffering the full body. A request body may be buffered up to 32 MB; if it exceeds the limit, the connection is dropped.
• A response body may be modified only up to 1 MB on iOS and 10 MB on macOS. If the response exceeds the limit, Surge gives up the modification and streams the response through unmodified.
• Request body rewrite is not supported when the request uses Transfer-Encoding: chunked or Expect: 100-continue. Surge logs a warning and forwards the request unmodified.
• When the body is modified, Surge normalizes the related headers automatically: the body is decompressed first if necessary, and Content-Length is recalculated.