--- title: "FastAPI" description: "Generate dynamic OG images and on-demand graphics in FastAPI with the Imejis.io API. A secure async endpoint that keeps your API key server-side and returns a cached image." url: "https://www.imejis.io/apis/fastapi" published: "2026-07-27" --- # FastAPI ## FastAPI Generate a unique OG image for every page, or any on-demand graphic, from a single Imejis template. The pattern below uses a FastAPI **endpoint** as a thin proxy: your API key stays on the server, and the browser (and social crawlers) only ever see your own URL. Set two environment variables first: `IMEJIS_API_KEY` (from your dashboard) and `IMEJIS_DESIGN_ID` (any design's ID). ```bash title=".env" IMEJIS_API_KEY=your_api_key IMEJIS_DESIGN_ID=your_design_id ``` ### 1. An endpoint that renders the image This endpoint takes a `title` query param, POSTs it to Imejis as a `component.property` override, and returns the finished image bytes. It uses `httpx` for a non-blocking request, and because the key is sent server-side it never reaches the client. ```python showLineNumbers title="main.py" import os import httpx from fastapi import FastAPI, Response app = FastAPI() @app.get("/og") async def og_image(title: str = "Untitled"): async with httpx.AsyncClient() as client: response = await client.post( f"https://render.imejis.io/v1/{os.environ['IMEJIS_DESIGN_ID']}", headers={ "dma-api-key": os.environ["IMEJIS_API_KEY"], "Content-Type": "application/json", }, json={"headline.text": title}, ) response.raise_for_status() return Response( content=response.content, media_type="image/jpeg", # Renders are deterministic, so cache aggressively at the edge/CDN. headers={"Cache-Control": "public, immutable, no-transform, max-age=31536000"}, ) ``` ### 2. Point your metadata at it Reference the endpoint from your page's ``, passing each page's real data. Social platforms fetch `/og?title=…` from your own domain, no key exposed. ```html showLineNumbers title="template.html" ``` **Override any field.** Each dynamic component exposes keys like `headline.text`, `title.color`, or `image.image`. Send only the ones you want to change. A design's overridable fields are listed in its Share / API panel.