metadata

title: REST API with Gradio and Huggingface Spaces
emoji: 👩‍💻
colorFrom: blue
colorTo: green
sdk: gradio
sdk_version: 5.34.2
app_file: app.py
pinned: false
license: openrail

Dynamic Space Loading

1. Sending Data To/From IFrames

A. Standard Web (HTML/JS) Context

IFrames are sandboxed: By default, an iframe is isolated from the parent page for security reasons.
postMessage API:
- The standard way to communicate between a parent page and an iframe (and vice versa) is using the window.postMessage API.
- This requires both the parent and the iframe to have JavaScript code that listens for and sends messages.
- Example:
  - Parent: iframeEl.contentWindow.postMessage({data: "hello"}, "https://iframe-domain.com")
  - IFrame: window.parent.postMessage({data: "hi back"}, "https://parent-domain.com")
Limitations in Gradio:
- Gradio does not expose a built-in way to inject custom JS for postMessage into the iframe or parent.
- If you control both the parent and the iframe (i.e., both are your own apps), you could add custom JS to both and use postMessage.
- If the iframe is a third-party app (like a Hugging Face Space you don’t control), you cannot inject JS into it, so you cannot send/receive data programmatically.

B. Gradio Context

No built-in Gradio API for iframe communication.
You can use gr.HTML to inject a script into the parent, but you cannot inject into the iframe if you don’t control its code.

2. Sending Data Between Tabs in Gradio

Tabs in Gradio are just layout elements: All components in all tabs exist in the same Python process and can share state.
You can use gr.State or any shared variable:
- For example, you can have a gr.State object that is updated in one tab and read in another.
- You can also use hidden components or callbacks to pass data between tabs.

3. Summary Table

Method	Parent ↔ IFrame	Tab ↔ Tab (Gradio)
postMessage (JS)	Yes (if you control both)	N/A
gr.State	No	Yes
Hidden Components	No	Yes
gradio API	No	Yes

4. Practical Recommendations

For arbitrary Hugging Face Spaces in iframes:
- You cannot send/receive data programmatically unless the Space itself is designed to listen for postMessage.
For your own Spaces:
- You can add JS to both parent and iframe to use postMessage.
For Gradio tabs:
- Use gr.State or shared components for seamless data transfer.

If you want a code example for tab-to-tab data sharing, or want to explore advanced iframe communication (with custom JS), let me know!