About Query String Builder

Build ?k=v&k=v strings from key=value lines — repeating keys OK. Part of the DevTools Surf developer suite. Browse more tools in the Networking collection.

Use Cases

• Frontend devs constructing complex API request URLs
• QA testers building URLs with multiple filter parameters
• Backend devs debugging query string parsing edge cases
• API integrators assembling webhook callback URLs with metadata

Tips

• Enter key=value pairs one per line for fast building
• Duplicate keys are preserved for multi-value parameters
• Output is automatically URL-encoded for safe pasting

Fun Facts

• The query string format (key=value&key=value) was defined in RFC 3986 (2005) by Tim Berners-Lee, though the convention existed informally since the earliest web forms in 1993.
• The maximum URL length varies by browser — Chrome supports up to 2MB, while Internet Explorer famously limited URLs to 2,083 characters.
• The '+' sign in query strings represents a space (from HTML form encoding), while %20 is the URI-standard encoding — this inconsistency still causes bugs today.

FAQ

How does it handle repeating keys?

Supports both styles: `?tag=a&tag=b` (repeated) and `?tag[]=a&tag[]=b` (bracket notation). Toggle based on what your server expects.

Are values URL-encoded?

Yes, automatically. Special characters (space, &, =, #) are percent-encoded. Toggle off only when debugging raw input.

What about nested objects?

Flat key-value by default. For nested, use bracket notation (user[name]=alice) or JSON encoding — both available.

Does it include the leading `?`?

Toggleable — include when appending to a base URL, omit when concatenating with existing query strings.