How do evergreen countdown timers work, and which merge tag do I use?
An evergreen countdown gives each recipient their own deadline — “24 hours from when you first opened this” — instead of one shared date. The mechanism is simpler than it sounds, and the only platform-specific part is which merge tag identifies the recipient.
The mechanism: a duration plus a recipient key
Two parameters do the work. A duration says how long the window is, in seconds. A recipient key — any value that is stable for that person — tells the renderer whose window this is. The first time a given key is seen, the clock starts; every later request with the same key counts down from that first moment. That is why the key must be stable and unique per person: reuse it and two people share a deadline, change it and the countdown restarts.
https://tikio.io/e/a1b2.gif?duration=86400&uid=*|UNIQID|* The merge tag for your platform
Each ESP has its own syntax for the recipient identifier. Use an internal ID where the platform offers one — it is stable and, unlike an email address, does not put personal data into an image URL. Where only the email address is available, that works too.
| Email platform | Recipient key to use |
|---|---|
| Mailchimp | *|UNIQID|* |
| Klaviyo | {{ person.id }} |
| HubSpot | {{ contact.hs_object_id }} |
| SendGrid | {{contact_id}} |
| ActiveCampaign | %SUBSCRIBERID% |
| Brevo | {{ contact.ID }} |
| Braze | {{${user_id}}} |
| Kit (ConvertKit) | {{ subscriber.id }} |
| Customer.io | {{customer.id}} |
| Iterable | {{userId}} |
| Adobe Marketo Engage | {{lead.Id}} |
| Salesforce Marketing Cloud | %%SubscriberKey%% |
| Keap | ~Contact.Id~ |
| beehiiv | {{subscriber_id}} |
| GetResponse | [[email]] |
| MailerLite | {$email} |
| Campaign Monitor | [email] |
| AWeber | {{ subscriber.email }} |
| Drip | {{ subscriber.email }} |
| Omnisend | [[contact.email]] |
| Unisender | ${user_id} |
Where evergreen is the right choice — and where it is not
Use it wherever recipients arrive at different times: drip sequences, onboarding flows, abandoned-cart automations, evergreen funnels. Do not use it for a broadcast to your whole list about a real, shared deadline — there a fixed date is both simpler and more honest, and a personal countdown would actively misrepresent the offer.
The one caveat worth knowing
Because the window opens at first open, anything that fetches images before a human reads the email can start the clock early — Apple’s Mail Privacy Protection is the main case. Over a 24- or 72-hour window this rarely matters; for a window measured in hours, prefer a fixed deadline.
FAQ
What if the merge tag does not resolve?
The countdown falls back to behaving like a shared timer rather than breaking. Always send yourself a test with a real contact and confirm the tag has been replaced with an actual value in the image URL.
Is it safe to put an email address in the URL?
It works, but prefer an internal ID when the platform exposes one — it keeps personal data out of URLs that get logged along the way. tikio also supports signing the key so it cannot be guessed or tampered with.
Can a recipient reset their countdown by clearing something?
No. The start time is recorded server-side against the key, not stored in the reader’s browser or client, so reopening on another device shows the same remaining time.
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Last updated: 2026-08-01.