The short version
- Two questions decide it: does the URL still need to work? and should the signals be kept or discarded?
- 301: the URL should stop existing. Visitors move, signals transfer, decisively.
- Canonical: both URLs must keep working, but one should be indexed. Signals consolidate, as a hint.
- noindex: the page is useful to visitors and should not be in search results at all.
- Combinations cancel: noindex plus a robots.txt block, or a canonical on a blocked page, both achieve nothing.
Why the choice matters more than the syntax
All three of these are easy to implement. None of them is easy to choose, and the consequences of choosing badly are not symmetrical.
Redirect a page that people still needed and you have removed something useful and thrown away a working URL. Canonicalise a page that should have been redirected and you keep a duplicate alive that Google may decide to index anyway. Noindex a page you meant to consolidate and you discard its accumulated signals entirely rather than passing them anywhere.
So the syntax is the last five minutes of the job. The decision is the job.
The two questions
Question 1: does this URL still need to work?
If no — it is an old address, a retired product, a page that moved — use a 301 redirect. Stop reading; that is the answer.
If yes — people use it, it is linked, it serves a purpose — continue to question two.
Question 2: should its ranking signals be kept or discarded?
Kept and pooled elsewhere — because this is a variant of another page — use a canonical.
Discarded — because this page has no business appearing in search
at all — use noindex, follow. The follow matters: it
keeps link equity flowing through the page to whatever it links to, rather than dead-ending
it.
What each one actually does
| 301 redirect | Canonical | noindex | |
|---|---|---|---|
| Visitor | Moved to the new URL | Stays where they are | Stays where they are |
| Old URL | Stops serving content | Keeps working | Keeps working |
| Signals | Transferred | Consolidated (as a hint) | Not passed on |
| Strength | An instruction | A strong suggestion | An instruction |
| Reversible | Yes, but slowly | Yes, quickly | Yes, quickly |
| Typical use | Page moved or retired | Duplicate that must stay live | Useful page, not for search |
The row that matters most is “strength”. A canonical is advisory: Google weighs it against your internal links, your sitemap and your redirects, and if those disagree it will follow the majority. Redirects and noindex are not advisory. This is why a canonical needs the rest of your site to agree with it, and the other two do not.
Free tool · One line, done right
Get the tag right, including the parts people get wrong
Paste the URL you want indexed. The generator normalises it and flags the usual killers — http instead of https, tracking parameters left on, a trailing slash that does not match your site.
Eight worked examples
1. You changed a URL structure
301. The old address should not survive. Redirect it, update your internal links to point at the new one directly rather than through the redirect, and update your sitemap.
2. A campaign landing page with UTM variants
Self-referencing canonical to the clean URL. The tagged variants must keep working — that is the entire point of tagging — and their signals should pool on the clean page.
3. Your thank-you page after a form submission
noindex, follow. It must work for the person who just submitted the form and has no business in search results. Left indexable, it will eventually rank for your brand name and confuse people who never filled in anything.
4. Internal search results pages
noindex, follow, and consider blocking the path in robots.txt too — but not both on the same URL, for reasons in the next section. Infinite, thin, and occasionally embarrassing.
5. A product available in three categories at three URLs
Canonical to whichever is the primary path. All three need to work for navigation; only one should be indexed.
6. You republished your article on Medium
Cross-domain canonical on the Medium copy, pointing back to your original. You control neither the platform nor the URL, so the canonical is the only available mechanism.
7. Two old blog posts that say almost the same thing
Merge, then 301. Combine the useful content into one stronger page and redirect the weaker URL to it. A canonical here leaves two mediocre pages alive when one good page was available.
8. A staging or client-preview site
None of the three. Use HTTP authentication. A noindex tag can be forgotten, a robots.txt can be deployed to production, and both are weaker than a password.
Use these together
- Robots.txt Generator — Build a valid robots.txt with the right allow, disallow and sitemap directives — and understand each one.
- SEO Page Checker — Check any live page for title, description, headings, canonical, robots, alt text and internal links.
- Sitemap URL Checker — Fetch an XML sitemap and check it is valid, reachable and free of the usual structural mistakes.
- The full set of twelve — free, no signup, and for nine of them nothing you type leaves your browser.
Combinations that cancel out
These look thorough and achieve nothing
- noindex + blocked in robots.txt — the crawler cannot fetch the page, so it never reads the noindex. The page can stay indexed as a bare URL indefinitely.
- Canonical + blocked in robots.txt — same mechanism. The tag is in a document nobody is allowed to read.
- Canonical + noindex on the same page — contradictory instructions. One says “credit this other page”, the other says “drop this entirely”. Google resolves it unpredictably; pick one.
- Canonical pointing at a redirect — you named a URL that does not return 200. The signal weakens and may be discarded.
- 301 chains — A to B to C to D. Each hop loses a little and adds latency. Point every old URL directly at the final destination.
The pattern in all five: the instruction was correct and the delivery mechanism was blocked. Whenever you combine two of these techniques, ask whether the second one prevents the first from being read.
Once you have decided
If it is a canonical, the canonical tag generator produces the line, normalises the URL, and flags protocol mismatches, leftover tracking parameters and trailing-slash inconsistencies — the three things that quietly make a present canonical useless. Free, in your browser, nothing stored.
If it is a noindex, the meta tag generator writes the robots directive alongside the rest of the head block, so it goes in with everything else rather than being added as an afterthought.
If it is a redirect, that lives in your server configuration, your CMS or your hosting platform — there is no tag to generate. What you can do afterwards is verify: the SEO page checker reports the status code and the canonical actually being served, which is how you find out whether the redirect chains, whether the canonical survived your plugin, and whether the page returns 200 at the URL you think it does.
Then update your sitemap. A sitemap listing URLs you have just redirected or noindexed is sending crawlers to pages you have told them to ignore, which is a contradiction they will resolve by trusting you less.
FAQ
When should I use a 301 instead of a canonical?
When the old URL should stop existing. A 301 moves the visitor and transfers signals decisively, and it is not something Google can decline. Use a canonical only when both URLs genuinely need to keep serving content.
Does noindex pass link equity?
Use noindex, follow and links on the page continue to be followed, so
equity flows through to the pages it links to. noindex, nofollow
dead-ends it. In almost every practical case you want follow.
Can I use a canonical and a noindex on the same page?
You can technically, and you should not. They give contradictory instructions — one asks Google to credit another URL, the other asks it to drop this one entirely. Google resolves the conflict in ways that are hard to predict. Decide which outcome you want and use only that tool.
How long does a 301 take to take effect?
For visitors, immediately. For search results, days to weeks as Google recrawls and processes it. Keep redirects in place permanently, or at minimum for a year — removing them later resurrects every 404 you had already solved.
Is duplicate content a penalty?
No. There is no duplicate content penalty in the sense people mean. What happens is dilution: signals split across variants, and Google picks a representative URL that may not be the one you wanted. These three tools exist to make that choice yours rather than its.
Thejas Acharya
Digital growth consultant based in Bangalore, working with founders and marketing teams across India and the US. I build websites, landing pages, Meta Ads campaigns and AI automation that are judged on one thing: whether they generate leads. The free tools on this site are the checks I run on client work, opened up.