A query string is the part of a URL after ? that passes data to the server. Format: key=value, multiple params separated by &.
Common Uses:
β’ UTM tracking β track traffic sources in Google Analytics
β’ API requests β pass filtering, sorting, and pagination to REST APIs
β’ Referral links β share referral codes and source information
β’ Page state β preserve filter selections and search terms
Special characters (spaces, Chinese, &, =, etc.) are URL-encoded automatically (space becomes %20). Use "Copy Encoded URL" for the fully encoded version.
UTM parameters can create duplicate content issues. Use Google Search Console's URL parameter tool to set handling rules, or restrict UTM-parameter URLs in robots.txt.
There's no hard limit, but browsers and servers typically limit total URL length to 2048-8000 characters. Keep it concise and remove unnecessary params.