Three tools say "last click". Each one means a different click

When two reports both say “last click” and still disagree, the usual suspicion is a broken tag. Usually the tag is fine. The two tools are applying two different rules under one name.

Last click is not one attribution model. It is a family of them, and each tool’s version credits the last touch that tool is allowed to credit. Google Ads picks the last Google ad clicked. GA4 picks the last click of any kind, except a direct visit. LinkedIn picks the last LinkedIn ad clicked or seen. Put one buyer through all three and you get three answers.

What “last” means in each tool

Read from each tool’s own help pages on 12 October 2026. Every cell is in facts above with its source.

Tool	Default model	Its last-click rule	Can the winning touch be a view?	Who is eligible
Google Ads	Data-driven, for most conversion actions	Last click: all credit to the last-clicked ad and its keyword	No	Google ads only (Google Paid is the default for Google Ads reports)
GA4, paid and organic last click	Chosen per property in Attribution settings; data-driven is the only other option	100% to the last channel clicked through. Direct visits are ignored	Only a YouTube engaged view	Paid and organic channels (the GA4 report default)
GA4, Google paid channels last click	—	100% to the last Google Ads click. No Google Ads click? Falls back to the rule above	Only a YouTube engaged view	Google Ads channels first
LinkedIn	Last touch, for most conversion types	The most recent LinkedIn ad click or view in the window	Yes, within a 90-day view window by default	LinkedIn ads only

First click, linear, time decay and position-based are gone from both Google Ads and GA4. What is left in Google’s tools is data-driven or one of the last-click variants.

Two tools are missing on purpose. Microsoft Advertising’s help index has no page that describes an attribution model for click conversions, so there was no rule to read. Meta’s help centre renders in the browser and gave no article text to a fetch. A blank is better than a rule copied from someone else’s summary.

One buyer, three answers

Take one purchase, and run it through each tool’s documented rule:

1. Day 1: clicks a Google search ad.
2. Day 3: is served a LinkedIn Sponsored Content ad. Does not click.
3. Day 4: clicks an organic Google result.
4. Day 5: types the URL and buys.

The whole path takes five days. That is inside Google Ads’ default 30-day click window, GA4’s 90-day lookback and LinkedIn’s 90-day view window. Here is who gets the sale:

Report	Rule applied	Credit goes to
Google Ads, last click	Last-clicked Google ad	The day-1 search ad. 1 conversion
LinkedIn, last touch	Most recent LinkedIn click or view	The day-3 view. 1 conversion
GA4, paid and organic last click	Last click, direct ignored	Organic Search. Paid media gets 0
GA4, Google paid channels last click	Last Google Ads click	Paid Search

The ad platforms report two conversions for one sale. GA4, on its default channels, gives paid media none of it. Not one of these four numbers is a bug. The Google Ads report cannot see the organic click. LinkedIn cannot see either Google click. GA4 cannot see the LinkedIn impression at all.

Switch the Google Ads conversion action to its default, data-driven, and nothing changes here: there is only one Google ad in the path, so it takes 100% either way.

It gets worse inside a single tool. Suppose the buyer saw ads from two LinkedIn ad sets. Under Last touch - Each ad set, every ad set with an interaction in the window is credited. LinkedIn says it does not deduplicate conversions between ad sets. So one sale can show up as two LinkedIn conversions before you add any other platform.

Why the name causes the mix-up

“Last-click attribution” sounds like a property of the journey. It is a property of the tool. Each tool can only rank the touches it observed, and each one has its own rule for which touches count. Ask “what was the last click?” and each tool gives you its own answer.

This is also why GA4’s report total is lower than the sum of the platform totals. GA4 hands each sale to one channel. Each ad platform claims every sale it touched. That gap is not missing data. It is the difference between one ledger and several.

What to do differently

1. Name the variant, not the family. “Last click (GA4, paid and organic, direct ignored)” and “last touch (LinkedIn, views included, 90-day view window)” are two different measurements. Write them that way on every slide.
2. Use one tool’s last click to compare channels. If you compare channels on last click, take every channel’s number from the same tool. A Google Ads conversion next to a LinkedIn conversion compares two rules, not two channels.
3. Check LinkedIn’s ad-set setting before you sum ad sets. Under Each ad set, the ad-set rows can add up to more conversions than happened.
4. Treat agreement between tools as a coincidence, not proof. Two last-click reports match only when the last touch was a click every tool could see. That tells you about the path, not about what caused the sale. Causation is an incrementality question, and a holdout test answers it.