Keep your tracking code. Get told what to fix.

The idea that dies in the meeting

You want to know why people leave at checkout. Then an engineer says it: "We would have to tag every event again. Two sprints, maybe three." The idea stops there.

Sequential does not start with a new SDK. It starts with yours.

What you get: findings, not recordings

Illustrative example: Northlight Outfitters is a fictional shop.

Northlight points its posthog-js at Sequential and adds the recorder line. By Wednesday the head of product has a finding: a request on the shipping page fails. It hit 38 people. Sample sessions show the moment.

The team’s agent files it as WEB-231 in their tracker and links it to the finding. Sequential does not file tickets.

A developer ships the fix in release 2026.10.09 and records the release in Sequential. Sequential then measures the shipping page again: 41% → 12% of sessions. This is a measurement, not a statement about why.

• One model for every SDK. Sequential sorts each event into one of nine classes when it arrives. So analytics, replay and session judging work the same for each SDK.
• Evidence you can check. Each finding counts the people who hit the problem. It links up to five sample sessions. Each one plays from the moment the problem occurred.

Switching is a change to your config

1. 01

   Change two values.

   In your current init, put in your Sequential key and host, or change their environment variables. Your capture, track and identify calls do not change. For Pendo, add one line and register your Pendo API key in Sequential.

2. 02

   Add one line for replay.

   On the web, PostHog, Mixpanel, Amplitude and Pendo use the Sequential recorder script. It reads the session id of your SDK, so your events show on the replay timeline. You do not fork your SDK or add a second analytics SDK. sequential.js and the Smartlook script start the recorder themselves.

3. 03

   See it receive.

   Your project’s Setup page changes from "no events yet" to "receiving". Events usually show within about a minute.

Which SDKs, and what each one gives you

• In the browser. PostHog, Mixpanel, Amplitude and Pendo.
• Smartlook. Put in the address of the Sequential compatible script and your key. Your tracking calls keep working.
• Mobile. PostHog’s open-source iOS and Android SDKs send events and screen recordings to Sequential. We tested iOS with a real app in the simulator. Android uses the same protocol and is not tested yet.

We publish what each SDK gives you: 7 sources and 11 capabilities. Each cell is Yes, Partial or No, with a note that tells you why. Two of the rows:

• Session replay. Yes for the Sequential SDK, PostHog (mobile) and Smartlook. Partial for PostHog (web), Mixpanel, Amplitude and Pendo.
• Feature flags, surveys, experiments. No for every source.

Partial means that Sequential does not accept the vendor’s own web recording. So you add the Sequential recorder line. That line also gives DevTools to every web source.

You keep the tracking you have. Sequential turns what it sends into answers.

No analytics yet? sequential.js is our own tag: analytics and replay in one script, under 20 KB gzipped.

Or give the switch to your coding agent

Each install page in the docs has a Copy prompt button. Your coding agent finds the SDK in your repo and edits the init that you have. When you are signed in, the prompt has your keys in it.

• The agent never adds a second SDK.
• It changes only the values in the list.
• If your app uses PostHog feature flags, it stops and tells you first.

# .env.production
- VITE_POSTHOG_KEY=phc_…
- VITE_POSTHOG_HOST=https://eu.i.posthog.com
+ VITE_POSTHOG_KEY=sq_posthog_…
+ VITE_POSTHOG_HOST=https://api.usesequential.com

# index.html
+ <script src="https://api.usesequential.com/rec/recorder.js/sq_replay_…"></script>

The agent report: "Changed .env.production and added the recorder line. Not checked: live requests. Sequential turns automated browsers away as bots, so check Setup from a normal browser." You read the diff and approve it.

Good to know

• You move over. Each SDK sends its data to one place. So you move over; you cannot send the same SDK to your vendor and to Sequential at the same time. Do not run sequential.js next to a vendor SDK: each page view would count two times.
• Vendor extras stop. PostHog flags evaluate as off, Pendo guides stop and Amplitude Experiment is not supported. Sequential does not have its own.
• History starts on the day you switch. Your data in Sequential starts on the day you switch. Sequential cannot import recordings or history from your vendor.
• No server-side events. Sequential does not accept server SDKs.
• Mobile means PostHog’s SDKs. We tested iOS with a real app in the simulator. Android uses the same protocol and is not tested yet. React Native and Flutter are accepted, not yet verified. Mixpanel, Amplitude and Smartlook mobile SDKs are not supported.
• Pendo is our least tested source. We built it to Pendo’s documented format. We have not yet run it against a live subscription. Make sure that it works on the Setup page.
• Trademarks. PostHog, Mixpanel, Amplitude, Pendo and Smartlook are trademarks of their owners. Sequential is not affiliated with them.

Questions