5.8 Customize Swagger

If you want to change that “FastAPI 0.1.0 OAS 3.1 /openapi.json” header in Swagger UI, you can override it by customizing FastAPI’s title, version, and swagger_ui_parameters.

The simplest approach is to set title and version when creating your FastAPI app:

from fastapi import FastAPI

app = FastAPI(
    title="My Custom API Docs",
    version="2.5.7",
    description="Custom Swagger UI header example",
    swagger_ui_parameters={"docExpansion": "none"}
)

This will make Swagger UI show:

My Custom API Docs
2.5.7
OAS 3.1
/openapi.json

---

If you want to remove the OAS 3.1 /openapi.json bit

FastAPI itself doesn’t expose a direct parameter to remove that part, but you can override the Swagger UI HTML template:

from fastapi import FastAPI
from fastapi.openapi.docs import get_swagger_ui_html

app = FastAPI(docs_url=None)  # Disable default docs

@app.get("/docs", include_in_schema=False)
async def custom_swagger_ui_html():
    return get_swagger_ui_html(
        openapi_url="/openapi.json",
        title="My Custom API Docs",
        swagger_favicon_url="https://example.com/favicon.ico",
        swagger_js_url="https://cdn.jsdelivr.net/npm/swagger-ui-dist/swagger-ui-bundle.js",
        swagger_css_url="https://cdn.jsdelivr.net/npm/swagger-ui-dist/swagger-ui.css"
    )

Then you could tweak the CSS or JS in that template to hide or replace the header line entirely.

---

If you want, I can give you a version that fully hides the /openapi.json and OAS 3.1 display so it only shows your API name. That requires adding one small CSS override.