A query string is the part of a URL that comes after the question mark, containing data passed to the webpage. For example, in “example.com/search?q=web+design&type=blog”, everything after the ”?” is the query string. It’s used to pass information to the server or track visitor behaviour.
How Query Strings Work
Query strings consist of key-value pairs separated by ampersands (&). Each pair has a parameter name and value connected by an equals sign (=). Spaces are typically replaced with plus signs (+) or encoded as %20. Special characters are URL-encoded to avoid conflicts.
Common Uses
Search functionality - Passing search terms to results pages. Filtering and sorting - Allowing users to filter products or sort lists. Tracking campaigns - UTM parameters tracking where visitors came from. Session management - Maintaining state across pages. Sharing specific views - Allowing users to share filtered or customised page states.
Query Strings in Marketing
UTM parameters are query strings used to track marketing campaigns. “utm_source” identifies where traffic came from. “utm_medium” specifies the marketing medium (email, social, etc.). “utm_campaign” names the specific campaign. Analytics tools use these to attribute traffic and conversions to campaigns.
SEO Considerations
Search engines can struggle with URLs containing query strings. Multiple URLs with different query strings but similar content can create duplicate content issues. Use canonical tags to indicate the preferred version. Consider using URL rewriting to create cleaner URLs. Set parameters in Google Search Console to tell Google how to handle them.
Security Concerns
Never pass sensitive information in query strings, they’re visible in URLs. Browser history and server logs store query strings. Third-party websites see query strings in referrer data. Use POST requests for sensitive data instead. Sanitise and validate all query string inputs to prevent security vulnerabilities.
Query Strings vs. URL Paths
URL paths (/category/product/) are generally preferred for permanent content structure. Query strings work better for temporary states or filters. Paths are more SEO-friendly and user-friendly. Query strings are more flexible for dynamic filtering. Consider your use case when deciding which to use.
Best Practices
Keep query strings short and readable. Use descriptive parameter names. Avoid exposing internal system details. Implement proper server-side validation. Use canonical tags to consolidate query string variations. Consider removing unnecessary parameters that don’t affect content. Document your query string parameters for maintenance.
Query Strings in Analytics
Most analytics platforms track query string parameters. This allows you to see which campaigns drive traffic. You can segment users based on query string values. Set up goals tracking conversions from specific parameters. Use query strings to test different traffic sources or messaging.