Canonical tag vs 301 redirect: which one do you need?

Use a 301 redirect when the old URL should stop existing, and a canonical tag when several URLs must stay reachable but one should count as the main version.

Both fix duplicate-URL problems, so founders mix them up. They do different jobs, and using the wrong one is a common way to confuse search engines.

What each one does

• A 301 redirect sends visitors and crawlers from one URL to another, permanently. The old address stops loading its own page.
• A canonical tag leaves every URL working and tells search engines which one is the main version. It is a hint, not a command, so search engines may choose differently.

Use a 301 redirect when

• You moved a page or renamed its address.
• You switched from http to https, or want one version of your domain (with or without www).
• Two pages say the same thing and you only want to keep one.

Use a canonical tag when

• The same page loads with tracking parameters, such as ?utm_source=newsletter.
• A list page can be sorted or filtered into many URLs that show mostly the same content.
• You publish a post elsewhere as well and want your own copy to count as the original.

<link rel="canonical" href="https://example.com/pricing">

Mistakes to avoid

• Mixed signals. Do not redirect page A to page B and then give page B a canonical pointing back at A.
• Canonical to a redirect or an error. The canonical should point at a normal page that returns a successful response.
• Pointing every page at the homepage. This can lead search engines to ignore the pages you care about. Each page should point to itself, unless it is a true duplicate.

A quick rule

If a visitor should never need the old address again, redirect it. If people or tools will keep using several addresses, keep them and add a canonical. When unsure, a self-referencing canonical on every page is a safe default.

In our free audits of 365 homepages, 137 of the 251 sites with two or more issues (55%) had no canonical tag. That is our own sample and not a base rate for the web, but it is the most common finding. Test yours with the canonical tag checker.

Check your own site

Marlo's free audit crawls your homepage and checks the title, description, headings, canonical and social tags, with the fix for each. No signup.

Written by Marlo's maker. Marlo is open source (AGPL-3.0) and the audit code is public.