---
description: Similar to Full Mode, but with added validation of the origin server’s certificate, which can be issued by a public CA like Let’s Encrypt or by Cloudflare Origin CA.
title: Full (strict)
image: https://developers.cloudflare.com/og-docs.png
---

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# Full (strict)

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/origin-configuration/ssl-modes/full-strict/index.md)|[Agent setup](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/agent-setup/)

When you set your encryption mode to **Full (strict)**, Cloudflare does everything in [Full mode](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/origin-configuration/ssl-modes/full/) but also enforces more stringent requirements for origin certificates.

flowchart LR
    accTitle: Full - Strict SSL/TLS Encryption
    accDescr: With an encryption mode of Full (strict), your application encrypts traffic going to and coming from Cloudflare.
    A[Visitor] <--Encrypted--> B((Cloudflare))<--Encrypted--> C[("Origin server (verified) #9989;")]

## Use when

For the best security, choose **Full (strict)** mode whenever possible (unless you are an [Enterprise customer](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/origin-configuration/ssl-modes/ssl-only-origin-pull/)).

Your origin needs to be able to support an SSL certificate that is:

* Unexpired, meaning the certificate presents `notBeforeDate < now() < notAfterDate`.
* Issued by a [publicly trusted certificate authority ↗](https://github.com/cloudflare/cfssl%5Ftrust) or [Cloudflare’s Origin CA](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/origin-configuration/origin-ca/).
* Contains a Common Name (CN) or Subject Alternative Name (SAN) that matches the requested or target hostname.

Note

In addition to **Full (strict)** encryption, you can also set up [Authenticated Origin Pulls](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/origin-configuration/authenticated-origin-pull/) to ensure all requests to your origin are evaluated before receiving a response.

## Required setup

### Prerequisites

Before enabling **Full (strict)** mode, make sure your origin:

* Allows HTTPS connections on port `443`.
* Presents a certificate matching the requirements above.

Otherwise, your visitors may experience a [526 error](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-526/).

### Process

To change your encryption mode in the dashboard:

1. In the Cloudflare dashboard, go to the **SSL/TLS Overview** page.  
[Go to **Overview** ↗](https://dash.cloudflare.com/?to=/:account/:zone/ssl-tls)
2. Choose an encryption mode.

To adjust your encryption mode with the API, send a [PATCH](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/api/resources/zones/subresources/settings/methods/edit/) request with `ssl` as the setting name in the URI path, and the `value` parameter set to your desired setting (`off`, `flexible`, `full`, `strict`, or `origin_pull`).

## Limitations

Depending on your origin configuration, you may have to adjust settings to avoid [Mixed Content errors](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/troubleshooting/mixed-content-errors/) or [redirect loops](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ssl/troubleshooting/too-many-redirects/).

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