How to Test REST & GraphQL APIs on Android

Why Would You Test APIs From Your Phone?

Fair question. If you have a laptop nearby, you probably wouldn't. But laptops aren't always nearby.

Maybe you're on call and something breaks at 11pm. Maybe you're commuting and want to quickly verify an endpoint. Maybe you're in a meeting and someone asks "is that API still returning 500?" and you'd rather check than guess.

Or maybe you just prefer not to open your laptop for a 5-second health check.

Whatever the reason — there aren't many good options on Android. Postman doesn't have a native Android app, and most popular alternatives are desktop or web-only. The few Android apps that do exist tend to cover the basics but fall short on auth, import, or handling anything beyond a simple GET request.

What Giant JSON Viewer's API Client Can Do

Giant JSON Viewer is primarily a JSON viewer — it's built to open multi-gigabyte JSON files on a phone without crashing. But along the way, it grew an API client that turned out to be surprisingly capable.

Here's what it supports:

HTTP Methods

GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS, and a dedicated GraphQL mode with a query + variables editor.

Request Body Types

JSON, plain text, GraphQL, form URL-encoded, multipart form data (with file attachments from your device), and raw binary upload.

Authentication

This is where most mobile API clients give up. Giant JSON Viewer supports:

• Basic Auth — username and password
• Bearer Token — paste your token
• API Key — in header or query parameter
• OAuth 2.0 with PKCE — full authorization code flow with token refresh. Yes, on a phone.
• AWS Signature V4 — for those of you talking to API Gateway, S3, Lambda, or any AWS service directly. Region, service, session token — it's all there.

Postman Collection Import

Import your existing Postman collections (v2.0 and v2.1) with full folder structure, nested requests, inherited auth, and collection variables.

cURL Import & Export

Paste a cURL command from Chrome DevTools, Firefox, or Stack Overflow. The parser handles single-quoted, double-quoted, and $'...' strings, line continuations from bash, CMD, and PowerShell, and auto-detects auth from Authorization headers. Export any request back as a formatted cURL command.

Environments & Variables

Create environments (Dev, Staging, Production) and use {{variables}} in URLs, headers, body, form fields, and even auth configuration. Variables resolve with Postman-compatible precedence: collection → environment → inline.

Network Metrics

Every request shows a detailed timing breakdown: DNS lookup, TCP connect, TLS handshake, time to first byte, and download duration. Useful for figuring out if it's the server being slow or the network being flaky.

Response Handling

Responses stream to disk instead of loading into memory. This means you won't get an out-of-memory crash even if an endpoint dumps a 200MB JSON response at you. And since this is Giant JSON Viewer — the response opens directly in the full JSON tree browser with search, filtering, and export.

A Few More Things

• Request History — every request is logged with timestamps
• Session Cookies — maintained across requests
• Configurable Timeouts — connect, read, and write
• Follow Redirects — toggle per request
• Request Cancellation — because sometimes you realize mid-flight that you hit the wrong endpoint

What It Does NOT Do

Being straight with you here — this is a feature inside a JSON viewer, not a full Postman replacement:

• No pre-request or test scripts — there's no JavaScript engine. If your workflow depends on scripting, this won't cover it.
• No WebSocket support — REST and GraphQL only.
• No Swagger/OpenAPI import — you can import Postman collections and cURL, but not raw API specs.
• No team collaboration — everything lives on your device. No cloud sync, no shared workspaces.

If you need those things, Postman on desktop is still the right tool. But if you need to fire off authenticated requests from your phone with real auth, real collections, and the ability to actually read the response — this does the job. And if you're working with HAR files, you can clone any captured request straight into the API Client for replay.

Frequently Asked Questions

Is there a Postman app for Android?

Postman does not have a native Android app. Giant JSON Viewer includes a REST and GraphQL API client for Android that can import Postman collections, making it a practical alternative for mobile API testing.

How do I test a REST API from my phone?

Install an API testing app like Giant JSON Viewer on your Android device. You can create requests manually, import them from cURL commands, or import entire Postman collections. Set up auth, configure headers and body, and tap send.

Can I import Postman collections on Android?

Yes. Giant JSON Viewer imports Postman collections in v2.0 and v2.1 format, preserving folder structure, request details, auth inheritance, and collection variables.

Does it support OAuth2 authentication?

Yes — the full OAuth 2.0 Authorization Code flow with PKCE, including token refresh. You can also use Basic Auth, Bearer tokens, API keys, and AWS Signature V4.

Can I test AWS APIs from my Android phone?

Yes. The API client supports AWS Signature V4 authentication with configurable region, service name, and optional session token for temporary credentials (STS).

What happens if the API returns a huge response?

Responses are streamed to disk, not loaded into memory. Even multi-hundred-megabyte JSON responses can be opened and navigated in Giant JSON Viewer's tree browser without crashing.