Content Decay or an Algorithm Update? How to Tell the Difference

The short version: the standard test — many pages on one date means an algorithm update, one page on a slow slide means decay — is unreliable, because core updates now take eleven to eighteen days to roll out. Over two weeks, an update draws a slope, not a step. The reliable check is Google's own: get the rollout's start and end date from the Search Status Dashboard, wait a full week after it finishes, then compare against a week before it began.

I've written the slope-versus-cliff rule myself, more than once, and it's a decent first instinct. It is also the thing that made me spend two weeks last year rewriting a page that hadn't done anything wrong. This is the version I'd give myself back then.

The two tests you've been given, and why both fail

Almost every article on this question hands you the same two heuristics. Both are approximations that break in the exact situation where you need them.

Test one: "an update hits on a single date." It doesn't. Google publishes the start and end time of every confirmed update on the Search Status Dashboard, and the durations are not what the advice implies:

Update	Started	Rollout took
June 2026 spam update	24 Jun 2026	2 days, 1 hour
May 2026 core update	21 May 2026	11 days, 21 hours
March 2026 core update	27 Mar 2026	12 days, 4 hours
December 2025 core update	11 Dec 2025	18 days, 2 hours
June 2025 core update	30 Jun 2025	16 days, 18 hours

A core update that takes twelve days to roll out doesn't produce a cliff in your chart. It produces a decline that starts somewhere in that window, deepens unevenly, and settles — which is a slope. Add Search Console's own reporting lag of a day or two and the picture gets blurrier still. For roughly three weeks, a core update and content decay make the same shape.

Test two: "an update hits your whole site." Often, but not reliably. Google's core updates guidance says the changes "are broad in nature, and don't target specific sites or individual web pages" — but broad means applied everywhere, not felt everywhere equally. Results get re-evaluated query by query. If your blog covers four topics, one topic can move while the other three sit still. On the Pages tab that reads as page-specific, and page-specific is the signature everyone tells you means decay.

So the two tests, used on their own, will tell you it's decay when it's an update and vice versa. The good news is that Google wrote the check that works and hardly anyone uses it.

The check that works, in five steps

This is Google's procedure, from the core updates doc, with the Search Console navigation filled in.

1. Find the update and note both dates. Open the Search Status Dashboard and look for a ranking update overlapping your decline. Write down the start and the end. The end date is the one nobody records and the one the rest of this depends on.
2. Wait a full week after it finishes. Google's wording is direct: it recommends "waiting at least a full week after a core update completes before analyzing your site in Search Console." On a twelve-day rollout that means you are looking at roughly three weeks of not knowing. That is annoying, and it is still the correct answer.
3. Compare the right two windows. Not last month versus this month. Google says to compare "this week with a week before the core update started rolling out." In the Performance report, turn on compare mode, choose Custom, and set the two ranges by hand — the built-in presets will straddle the rollout and hand you a meaningless average. (If compare mode is new to you, I walk it through click by click in how to find declining pages in Search Console.)
4. Judge it by the size of the position drop, not the clicks. Google draws the line in its own examples. A small drop — its example is position 2 to position 4 — needs nothing: "There's no need to take drastic action (in fact, we recommend avoiding making changes to content that's already performing well)." A large drop — its example is 4 to 29 — is worth a real assessment. My own working floor for calling any page decayed at all is a 1.0 position slip with clicks at least 20% below the eight-week baseline; below that I don't trust the number enough to act on it.
5. Split the search types. In the Performance report, Search type is a filter, not a given. A drop that lives entirely in Images or in the News tab is a completely different problem from one in web results, and averaging them hides it.

Run in that order, you get a real answer: if your page fell inside the rollout window and its neighbours in the same topic moved with it, it's the update. If it was already sliding for weeks before the start date, the update is not your explanation — it may have made things worse, which is the next section.

Two honest limits. The dashboard only lists confirmed updates, and Google ships unannounced changes constantly, so "no update on the dashboard" is weaker evidence than "there was one." And a manual action is a separate thing entirely — it shows up in the Manual Actions report in Search Console, it's rare, and it takes thirty seconds to rule out.

When it's neither

Before you accept either diagnosis, three cheap screens. Google's guide to debugging Search traffic drops covers all of them in more depth, and it's the right place to start if the drop is site-wide and sudden.

Seasonality. Search Console holds 16 months of data, which is exactly enough to compare this period against the same period last year. If the same dip is in last year's chart, nothing is wrong with your page. A recipe blog in January and a tax page in May are not decaying.

The noise floor. A page averaging six clicks a week can lose half its traffic to random variation. My rule is a 10 clicks per week baseline before a decline means anything at all — under that, the percentage is theatre.

Something you broke, or something Google mis-logged. A stray noindex, a redirect that stopped resolving, a robots.txt edit. Google's doc also points at its Data Anomalies page for the case where the drop is in the reporting rather than in reality. Both are worth ruling out before you write a single word of new copy.

The likeliest answer is both

The question is framed as either/or, and on most real sites it isn't. A page that has been quietly drifting — the topic moved, a competitor published something better, the results page started answering the query above you — is precisely the page a core update re-evaluates downward. The update didn't cause the decline. It priced it in, all at once.

You can usually see this. Pull the page's full 16 months and look at the shape before the rollout start date. Flat, then a step at the rollout, is an update landing on a healthy page. A slope that was already running for two or three months, then a step, is decay that got collected. The second is much more common, and it's the case none of the comparison articles handle — including the best one on the subject, Search Engine Land's four types of content decay, which files algorithm updates under "different playbook" and moves on.

If that's your chart, treat it as decay. The update is context, not a cause, and there's a real list of things that could be behind the slope — six of them, ordered by whether you can actually get the traffic back.

So what actually changes once you know?

Less than you'd hope, and that's the useful part.

If it's decay, you already have a workflow: find the pages, rank them by clicks per month at stake, diagnose the reason, change only what matches it, then measure. The five signatures decay makes in Search Console tell you which one you're looking at.

If it's an update, two things change, and neither of them is "rewrite the page tonight."

The first is timing. Google says improvements may take effect "in a few days, but it could take several months for our systems to learn and confirm that the site as a whole is now producing helpful, reliable, people-first content." It also says, usefully, that you "don't necessarily have to wait for a major core update to see the effect of your improvements" — the common belief that you're frozen until the next core update is not what the documentation says. But months is the honest planning number.

The second is priority, and this is the whole point of asking the question. If a page dropped two positions in an update, Google is telling you plainly to leave it alone. If it dropped twenty-five, the fix is a site-level quality argument that will take a quarter, not an afternoon. Either way, an update-hit page is a poor place to spend your next content hour compared with a page that is losing clicks for a reason you can name and fix this week. That's a budget decision, and it's the same one behind when not to refresh a post at all and which posts to update first — rank by clicks per month at stake, (baseline weekly clicks − recent weekly clicks) × 4.33, and work down.

And whichever it was, prove it afterwards: 28 days after against 28 days before. A page that recovers on its own during the next update, and a page that recovered because of your rewrite, look identical unless you wrote the baseline down first.

Know which pages were sliding before the update landed

Everything above runs in free Search Console, and the part that actually decides the diagnosis is the one nobody has: what the page was doing in the weeks before the rollout started. If you go looking for that after the drop, you're reconstructing it from memory and a 16-month chart.

That's the job RefreshRadar does. It watches every page in your Search Console every week, applies the same rules I use above — 20% below an eight-week baseline, above the 10-clicks-a-week floor, a 1.0 position slip — and emails you the ranked list with the clicks per month at stake on each. To be straight about the limits: it does not detect algorithm updates. There's no site-wide event screen in it, and the five steps above stay your job. What it gives you is the before picture, already recorded, so when a rollout lands you can tell in a minute whether that page was healthy the week before or had been sliding since May.

Connect Search Console read-only and see what's decaying on your site — free — no card, about 30 seconds, and we never post or change anything. You'll get your three worst-decaying pages with the reason on each. If nothing on your site is decaying, we'll tell you that instead.