API Field Mapper

What is API Field Mapper?

API Field Mapper is a free, browser-based tool that helps you get the job done quickly. Map fields between two API shapes. It's built for speed and privacy: Everything runs locally in your browser — your data is never uploaded to a server. No sign-up, no installs, and no daily limits.

Used by

• Backend developers
• API testers
• QA engineers
• Integration teams

Recommended workflow

1. 1

   Prepare the input

   Use this tool as the focused step in a larger browser-based workflow.

2. 2

   Run API Field Mapper

   Review the preview, copy or download the result, and keep everything local in your browser.

3. 3

   Next recommended tool

   API Response Formatter: Pretty-print and inspect API JSON.

   Open tool
4. 4

   Then continue with

   API Schema Extractor: Infer a schema from sample responses.

   Open tool
5. 5

   Then continue with

   JSON Response Analyzer: Inspect shape, types, and nesting.

   Open tool

Frequently asked questions

How do I use API Field Mapper?

Paste or drop your data into the workspace, adjust the options to fit your data, then copy or download the result. Map fields between two API shapes.

Is my data uploaded or stored anywhere?

No. Everything runs locally in your browser — your data is never uploaded to a server. Nothing is sent to a server, so it's safe to use with private or sensitive data.

Is API Field Mapper free?

Yes — it's completely free with no account, no sign-up, no watermark, and no daily usage limits.

What's the maximum file size?

There's no hard limit imposed by the tool. Because processing happens in your browser, the practical ceiling is your device's available memory — most everyday files work instantly.

Do I need to install anything?

No installs and no extensions — it runs entirely in your web browser and even works offline once the page has loaded.