midGraphQL
How and why do you use Variables in GraphQL?
Updated Apr 28, 2026
Short answer
Variables allow you to pass dynamic arguments to queries without manipulating the query string directly.
Deep explanation
Instead of concatenating strings to build a query (which is vulnerable to injection and ruins caching/parsing), you define variables in the query header (e.g., $id: ID!) and pass a separate JSON dictionary containing the values.
Real-world example
A search bar where the user's typed input is passed as a $searchTerm variable to the GraphQL query.
Common mistakes
- Using string interpolation (e.g., `user(id: "${userId}")`) which forces the server to re-parse the query every time instead of caching the AST.
Follow-up questions
- Can variables have default values?