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GraphQL Query Tester

A production-grade, client-side GraphQL playground. Test queries, mutations, and inspect schemas with header support, history management, and deep error analysis.

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Category Code Utilities
POST
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Response

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About

This GraphQL Query Tester is a specialized diagnostic environment designed for frontend engineers and backend architects who require an immediate, zero-latency interface for interacting with GraphQL endpoints. Unlike REST, where endpoints are resource-specific, GraphQL exposes a single endpoint that demands a strict schema adherence. This tool bridges the gap between raw HTTP requests and complex IDEs.

Accuracy in GraphQL integration is critical because errors are often buried in the errors array even when the HTTP status is 200 OK. This tool isolates the network layer, allowing you to debug CORS policies, Auth headers, and Schema Validation rules without the interference of application-level logic.

Core Constraints & Edge Cases: The browser's CORS (Cross-Origin Resource Sharing) policy is the primary limiter for client-side tools. If the target server does not allow requests from this origin, the browser will block the transaction before it reaches the network. This tool includes specific error handling to distinguish between network failures, CORS blocks, and valid GraphQL schema errors.

graphql api-client developer-tools debugging network

Formulas

The execution flow of a GraphQL operation involves three distinct phases before data is returned. Understanding this pipeline helps in debugging null results.

{
Phase 1: Parse → Validate Syntax (AST)Phase 2: Validate → Check Schema TypesPhase 3: Execute → resolve(obj, args, context)

When calculating the complexity of a nested query, the depth D often correlates to response latency L exponentially in poorly optimized schemas:

L ≈ k × d∑i=1 (Ni)

Where N is the branching factor (fields per node) and d is the recursion depth. Always inspect the extensions field in the response for tracing data if available.

Reference Data

CategoryHeader / ConceptStandard Value / DescriptionUtility
AuthAuthorizationBearer <token>Standard JWT/OAuth access method.
Authx-api-keyAlphanumeric StringCommon for public APIs (AWS AppSync, etc).
MIMEContent-Typeapplication/jsonStrictly required for GraphQL POST requests.
StructureoperationNameString (Optional)Identifies which query to run if multiple exist.
ErrorGRAPHQL_PARSE_FAILEDSyntax ErrorThe query string is malformed or brackets are unbalanced.
ErrorVALIDATION_ERRORType MismatchField does not exist on type or argument is invalid.
Introspection__schemaRoot FieldEntry point to query the type system of the API.
Introspection__typenameMeta FieldReturns the name of the object type at runtime.

Frequently Asked Questions

This is almost certainly a CORS (Cross-Origin Resource Sharing) issue. Browsers enforce security rules that desktop apps like Postman do not. If your server does not explicitly send the "Access-Control-Allow-Origin" header matching this domain, the browser blocks the response. You must configure your server's CORS settings to allow external origins or use a proxy.
This tool strictly supports "application/json" payloads for standard Queries and Mutations. It does not support the "multipart/form-data" specification required for the GraphQL Multipart Request Spec (file uploads). Testing uploads requires a client that constructs specific form boundaries.
Yes, provided they are defined within the same execution text block. The GraphQL engine parses the entire string sent. Ensure your fragment names are unique and referenced correctly in your selection set.
Ensure your Variables input is valid JSON (keys in double quotes) and that your Query definition declares the variables with the correct types (e.g., query GetUser($id: ID!) { ... }). If the variable names or types in the declaration do not match the JSON object keys, the server will reject the request.