Does c15t support Google-certified CMP like CookieYes?

No, per vendor docs. CookieYes documents Google-certified CMP support. c15t does not.

Do c15t and CookieYes block trackers before consent?

Neither leaked a tracker in the checks that ran. We could not run 1 of 4 checks for CookieYes. Each check loads the page. Then it looks for trackers that ran, cookies that the page set or data that left the page before the visitor chose.

c15t vs CookieYes: cookie banner speed and features compared

Results forFramework

On emulated mobile, c15t showed its banner sooner, in a median 240 ms against 2.42 s for CookieYes. CookieYes delayed the main content 232 ms less. Neither leaked a tracker in the checks that ran. We could not run 1 of 4 checks for CookieYes. Per vendor docs, only c15t offers open-source code. Per vendor docs, only CookieYes offers a Google-certified CMP.

c15tinth

c15t Tested: 3.0.0-alpha.10
All c15t results

CookieYesCookieYes

CookieYes Tested: Hosted
All CookieYes results

Which is faster, c15t or CookieYes?

Shorter bars are better. The exception is tracker blocking, where the bar shows the share of checks passed.

c15t and CookieYes on the mobile (emulated) profile, Next.js 16
Question	c15t	CookieYes	Difference
Banner appearsTime from navigation until the banner is visible on screen. Lower is better.	240 msFast	2.42 sFast	c15t’s banner appeared 2.18 s sooner.
Page slowed byExtra time before the main content paints (LCP), compared with the same page without a consent manager.	+408 ms95% interval 396 ms to 420 msSmall	+176 ms95% interval 148 ms to 212 msSmall	CookieYes delayed the main content 232 ms less.
Click responds inTime from pressing Accept until the screen updates. Under 200 ms feels instant.	32 msOne visit measuredFast	24 msOne visit measuredFast	About the same. They are less than 16 ms apart.
Blocks trackersChecks that no tracker runs, the page sets no cookie and no data leaves the page before the visitor chooses.	4 of 4 checks passedBlocked	3 of 4 checks passed1 could not be checkedPartly checked	Neither leaked a tracker in the checks that ran. We could not run 1 of 4 checks for CookieYes.
Adds to pageExtra data transferred during the first load, compared with the same page without a consent manager.	+112 KB95% interval: 112 KBModerate	+31 KB95% interval: 31 KBLight	CookieYes added 81 KB less to the first load.

“About the same” means that the two results fall within each other’s spread. We measure both against the same page without a consent manager. We do not publish a direct head-to-head interval yet.

Page vitals and load times

Lab detail for engineers. All values are medians on the mobile profile. Both CMPs ran on Next.js 16.

Page vitalsChange against the same page without a consent manager.
Metric	c15t	CookieYes
TTFB	+15 mspage 21 ms	No measurable delaypage 8 ms
FCP	+28 mspage 268 ms	No measurable delaypage 264 ms
LCP	+408 mspage 3.86 s	+176 mspage 3.64 s
CLS	No measurable shiftpage 0.00	No measurable shiftpage 0.00

Load timesMilliseconds from navigation.
Metric	c15t	CookieYes
CMP script requested
CMP script loaded
Consent state known	1.98 s
Banner visible	240 ms	2.42 s

After AcceptMilliseconds from the click.
Metric	c15t	CookieYes
Screen responds	32 ms	24 ms
Banner gone
Consent applied
Analytics active

Which features differ between c15t and CookieYes?

Statuses come from each vendor’s documentation. Each status links to its source.

Verified by test
Per vendor docs
Partial
Not supported
Unknown

Features that differ between c15t and CookieYes, from vendor docs
Feature	c15tc15t	CookieYesCookieYes
Only c15t · 2
Open sourceDeveloper	Apache-2.0 (vendor documentation, opens in a new tab)	Proprietary (vendor documentation, opens in a new tab)
First-party SDKsFrameworks	React, Next.js, Vue, Nuxt, Svelte, SvelteKit, Astro, TanStack Start (vendor documentation, opens in a new tab)	Script tag only (vendor documentation, opens in a new tab)
Only CookieYes · 1
Google-certified CMPStandards	Not on Google’s list (vendor documentation, opens in a new tab)	Per vendor docs (vendor documentation, opens in a new tab)
Not confirmed for one side · 4
IAB GPPStandards	GPP 1.1 (vendor documentation, opens in a new tab)	Unknown
Self-hostableDeveloper	Per vendor docs (vendor documentation, opens in a new tab)	Unknown
Headless UIDeveloper	Per vendor docs (vendor documentation, opens in a new tab)	Unknown
TypeScript typesDeveloper	Per vendor docs (vendor documentation, opens in a new tab)	Unknown

Same on both · 9

Features with the same status for c15t and CookieYes
Feature	c15tc15t	CookieYesCookieYes
IAB TCFStandards	Per vendor docs (vendor documentation, opens in a new tab)	Pro and Ultimate plans (vendor documentation, opens in a new tab)
Google Consent Mode v2Standards	Per vendor docs (vendor documentation, opens in a new tab)	Per vendor docs (vendor documentation, opens in a new tab)
Global Privacy ControlStandards	Per vendor docs (vendor documentation, opens in a new tab)	Pro and Ultimate plans (vendor documentation, opens in a new tab)
Geo-targeted bannersCompliance	Per vendor docs (vendor documentation, opens in a new tab)	Pro and Ultimate plans (vendor documentation, opens in a new tab)
Script blockingCompliance	Per vendor docs (vendor documentation, opens in a new tab)	Per vendor docs (vendor documentation, opens in a new tab)
Consent recordsCompliance	With a backend (vendor documentation, opens in a new tab)	Per vendor docs (vendor documentation, opens in a new tab)
Cookie scanningCompliance	Via Inth Website Audit (vendor documentation, opens in a new tab)	Per vendor docs (vendor documentation, opens in a new tab)
Free tierPricing	Open source; hosted free plan (vendor documentation, opens in a new tab)	5,000 pageviews a month (vendor documentation, opens in a new tab)
Script tagFrameworks	Per vendor docs (vendor documentation, opens in a new tab)	Per vendor docs (vendor documentation, opens in a new tab)

Should you choose c15t or CookieYes?

We built these lists from the measured and documented differences above. Neither list is a recommendation.

Choose c15t if

You want open-source code
You want a first-party SDK for React, Next.js, Vue, Nuxt, Svelte, SvelteKit, Astro and TanStack Start
A fast banner matters to you: c15t’s banner appeared 2.18 s sooner

Choose CookieYes if

You need a Google-certified CMP
Page load time matters to you: CookieYes delayed the main content 232 ms less
Page weight matters to you: CookieYes added 81 KB less to the first load

What was tested?

Deployment: Both ran as hosted services. c15t ran against the hosted inth backend, not a local mock. CookieYes ran from its vendor-hosted service. Network distance to each vendor is part of the result.

How we test: methodology cookiebench-v3.2.4