---
title: Block on TLS
description: Inspects the incoming request's TLS version and blocks if under TLSv1.2.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Block on TLS

Inspects the incoming request's TLS version and blocks if under TLSv1.2.

* [  JavaScript ](#tab-panel-11920)
* [  TypeScript ](#tab-panel-11921)
* [  Hono ](#tab-panel-11922)
* [  Python ](#tab-panel-11923)

JavaScript

```
export default {  async fetch(request) {    try {      const tlsVersion = request.cf.tlsVersion;      // Allow only TLS versions 1.2 and 1.3      if (tlsVersion !== "TLSv1.2" && tlsVersion !== "TLSv1.3") {        return new Response("Please use TLS version 1.2 or higher.", {          status: 403,        });      }      return fetch(request);    } catch (err) {      console.error(        "request.cf does not exist in the previewer, only in production",      );      return new Response(`Error in workers script ${err.message}`, {        status: 500,      });    }  },};
```

TypeScript

```
export default {  async fetch(request): Promise<Response> {    try {      const tlsVersion = request.cf.tlsVersion;      // Allow only TLS versions 1.2 and 1.3      if (tlsVersion !== "TLSv1.2" && tlsVersion !== "TLSv1.3") {        return new Response("Please use TLS version 1.2 or higher.", {          status: 403,        });      }      return fetch(request);    } catch (err) {      console.error(        "request.cf does not exist in the previewer, only in production",      );      return new Response(`Error in workers script ${err.message}`, {        status: 500,      });    }  },} satisfies ExportedHandler;
```

TypeScript

```
import { Hono } from "hono";
const app = new Hono();
// Middleware to check TLS versionapp.use("*", async (c, next) => {  // Access the raw request to get the cf object with TLS info  const request = c.req.raw;  const tlsVersion = request.cf?.tlsVersion;
  // Allow only TLS versions 1.2 and 1.3  if (tlsVersion !== "TLSv1.2" && tlsVersion !== "TLSv1.3") {    return c.text("Please use TLS version 1.2 or higher.", 403);  }
  await next();
});
app.onError((err, c) => {    console.error(      "request.cf does not exist in the previewer, only in production",    );    return c.text(`Error in workers script: ${err.message}`, 500);});
app.get("/", async (c) => {  return c.text(`TLS Version: ${c.req.raw.cf.tlsVersion}`);});
export default app;
```

Python

```
from workers import WorkerEntrypoint, Response, fetch
class Default(WorkerEntrypoint):    async def fetch(self, request):        tls_version = request.cf.tlsVersion        if tls_version not in ("TLSv1.2", "TLSv1.3"):            return Response("Please use TLS version 1.2 or higher.", status=403)        return fetch(request)
```

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