GraphQL gives a mobile app a flexible way to ask for exactly the data it needs, and that flexibility is also where its security concerns come from. A single endpoint exposes a whole graph of fields and resolvers, clients can shape arbitrary queries, and introspection can hand an attacker a map of your schema. The familiar API risks, authorization, injection, denial of service, all apply, but in GraphQL-specific forms. As with any API, the app is just one client and an attacker calls the endpoint directly, so the defenses live on the server. Here is what is distinct about securing a GraphQL mobile API.
Short answer
Securing a GraphQL API for a mobile app means addressing GraphQL-specific concerns on top of normal API security. Per OWASP's GraphQL guidance, the key ones are: introspection can expose your full schema, so restrict it in production; deeply nested or complex queries can exhaust server resources, so enforce depth and complexity limits, timeouts, and rate limiting; authorization must be enforced per field and object, not assumed from the schema; query batching and aliasing can multiply work and bypass naive rate limits; and resolver inputs must be validated to prevent injection. Because the app calls the endpoint and an attacker can too, all of this is enforced on the server.
What you should know
- One endpoint exposes a graph: many fields and resolvers behind a single URL.
- Introspection exposes the schema: restrict it in production.
- Complex queries can cause DoS: enforce depth and complexity limits.
- Authorization is per field and object: not assumed from the schema.
- Server-side enforcement: the attacker calls the endpoint directly.
What are GraphQL's distinct security concerns?
A handful that follow from its flexibility. The table lists them.
| Concern | Why it matters |
|---|---|
| Schema introspection | Exposes the full schema, mapping the API for an attacker |
| Query depth and complexity | Deeply nested queries can exhaust server resources |
| Batching and aliasing | A single request can multiply operations and bypass naive limits |
| Field and object authorization | Many resolvers each need access control |
| Resolver input injection | Inputs passed to a database or system can be injected |
The flexibility that makes GraphQL pleasant to consume, asking for arbitrary combinations of fields, is what creates these concerns: introspection lets a client, including an attacker, retrieve the schema; an expensive nested query can become a denial-of-service vector; and a single request can batch or alias many operations, multiplying work and slipping past rate limits that count requests rather than operations. Each field also has its own resolver, so authorization has to be enforced across all of them, not assumed because a field exists in the schema. These are the same risk families as in REST, in GraphQL-specific shapes.
How does authorization work in GraphQL?
Per field and per object, enforced in the resolvers. Because GraphQL exposes many fields through one endpoint, you cannot rely on the schema or the endpoint to gate access; each resolver that returns or modifies data must enforce that the requesting user is authorized for that specific field and object. This is where the same flaws seen in REST appear: broken object-level authorization, where a client requests an object it should not access, and over-returning fields a client should not see, both apply at the GraphQL field level. So authorization is not a single check at the endpoint but a consistent set of checks across your resolvers, confirming the user can access each object and field they request. A schema that exposes a field is not permission to read it; the resolver must verify access, the same principle as enforcing object-level authorization in a REST API.
How do you secure a GraphQL mobile API?
Restrict introspection, limit query cost, enforce authorization, and validate inputs, all server-side. Restrict or disable schema introspection in production so you are not handing out a map of your API. Enforce limits on query depth and complexity, set timeouts, and rate-limit, and account for batching and aliasing by limiting how many operations a single request can perform, so an attacker cannot multiply work or bypass per-request limits. Enforce authorization in your resolvers per field and object, confirming the user can access each thing they request, rather than trusting the schema. Validate resolver inputs and use parameterized queries where they reach a database, to prevent injection. And remember the app is just one client: an attacker calls your GraphQL endpoint directly, so every protection must be on the server, not in the app. The principle is to constrain what a single query can cost and what it can access, server-side.
What to watch out for
The first trap is leaving introspection enabled in production, which maps your schema for an attacker; restrict it. The second is no depth or complexity limits, letting an expensive query become a denial of service, and naive rate limiting that batching bypasses. The third is assuming the schema enforces authorization, when each resolver must check access per field and object. GraphQL security is enforced on your server, so a pre-submission scan such as PTKD.com (https://ptkd.com), which reads the binary against OWASP MASVS, surfaces the endpoints your app calls, including a GraphQL endpoint, as the surface to secure, while the resolver-level controls are yours to implement.
What to take away
- Securing a GraphQL mobile API means handling GraphQL-specific concerns: schema introspection, query depth and complexity, batching and aliasing, per-field authorization, and resolver input injection.
- Restrict introspection in production, enforce depth and complexity limits with timeouts and rate limiting, and limit batching so a single request cannot multiply work.
- Enforce authorization in resolvers per field and object, not from the schema, and validate inputs to prevent injection, all on the server.
- Use a pre-submission scan such as PTKD.com to inventory the endpoints your app calls, including GraphQL, then secure them server-side.
