Send Time in Klaviyo: Choosing the Right Strategy for BFCM

A Black Friday campaign is partly won or lost on the time it lands in the inbox. Klaviyo offers several ways to choose that time: a fixed send, a gradual send, a send at each recipient's local time, and two optimization tools, Smart Send Time and Personalized Send Time. Not all of them suit a time-limited offer.

TL;DR. For a time-sensitive BFCM send, Klaviyo's documentation advises against running Smart Send Time tests around important dates and against sending urgent content with it, and against Personalized Send Time for offers that expire. The simple options, fixed send, gradual send and recipient time zone, are available for all channels or nearly all. In our view, send-time optimizations should be tested in September or October, on campaigns with nothing at stake, not on Black Friday itself.

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Send now or schedule

Send now launches the send immediately, and delivery can take several minutes or more. Schedule picks a future time, with three strategies: fixed, gradual or Smart Send Time (Klaviyo, understand campaign scheduling and sending options).

Fixed-time send

All recipients get the email at roughly the same moment. The strategy is available for all channels. The page notes that sends can be a little slower at peak times (right on the hour, on the half hour) and advises entering an off-peak minute value to go faster, for example 3:04 PM rather than 3:00 PM. A processing delay of a few minutes exists anyway between the scheduled time and delivery.

Gradual send

The message goes out in batches: a percentage of recipients each time, until everyone has received it. You choose one batch per hour or per minute, with a share of 1% to 50% per batch. A send at 1% per minute delivers the campaign in 100 batches, or about 100 minutes. The page presents two uses: avoiding a spike of site traffic when recipients click, and pacing the send to support deliverability. This strategy is available for all channels, but not with an A/B test.

In our view, this is the option to look at for the Black Friday opening send: a large list clicking at the same time on a site already under strain. Your technical team knows better than we do what the store can handle, so the percentage per batch is something to decide with them.

Smart Send Time

Available for email only, and reserved for senders who meet certain criteria. We come back to it below.

Time zone: recipient or specific time zone

Depending on the strategy, two options exist.

• Recipient's local time zone: the campaign goes out at the chosen time in each person's time zone. At 3 PM, a Californian subscriber receives it at 3 PM PT and a British subscriber at 3 PM GMT. If a recipient's time zone is unknown, they receive the message in the account's time zone. For an A/B test, the option only appears for a 50/50 split.
• Specific time zone: everyone receives the message at the same moment, wherever they are.

If the scheduled time has already passed in a recipient's time zone, there are two choices: send immediately, or wait for the same time the next day. If you choose immediate sending, the time can no longer be changed after scheduling (Klaviyo, understand campaign scheduling and sending options).

For a French audience, this distinction matters little in our view within mainland France, since the time zone is the same. It matters if the list includes overseas territories or neighboring countries, or if an offer ends at a precise hour.

Who receives the campaign: the recipient snapshot

By default, Determine recipients at send time is turned off. Klaviyo then takes a snapshot of the list or segment at the moment you click Schedule campaign. People added or removed between scheduling and sending are not reflected. Most scheduled campaigns still filter out unsubscribed people before the send begins. When you turn the option on, Klaviyo takes a fresh snapshot as close to the send as possible, for emails, SMS and push notifications.

For campaigns sent in the recipient's time zone, the page is less clear. One passage says that a single snapshot is taken just before the send to the first time zone, and that someone who unsubscribes after that snapshot may still receive the campaign. Another passage says you cannot combine sending in the local time zone with determining recipients at send time, so no new recipients are added after scheduling. Both statements coexist on the page, so check in the interface what your account offers before building a plan on it.

For BFCM, this affects your audience segments: someone who joins the waitlist on Friday morning may not receive a campaign scheduled on Wednesday. Our article on BFCM audiences and exclusions returns to this point.

Smart Send Time: test it outside BFCM

Smart Send Time looks for the time that produces the most opens and clicks for your list. Klaviyo's model relies on a testing framework, and its results can be viewed (Klaviyo, understand Smart Send Time).

The conditions to know:

• Exploratory and targeted tests require an audience of 12,000 people or more, and an email billing plan that allows sending at that volume.
• The tool exists for email only.
• The send happens in the recipient's time zone. If Klaviyo is not sure of the time zone, the account time zone, set at the account level, applies.

Three phases follow one another. In the exploratory phase, the email is sent over 24 hours, with each person randomly assigned a time slot. The number of exploratory sends needed depends on audience size: 4 to 5 for 12,000 to 17,999 recipients, down to a single one above 72,000. In the targeted phase, one email goes out at the optimal time and two others within a two-hour window around it: if the model picks 7 AM, the groups receive the message at 5 AM, 7 AM and 9 AM in their time zone. Once the optimal time is found, it can be used for audiences of any size.

Above all, the page is explicit about timing: since the send happens at the recipient's local time, avoid urgent content, such as a flash sale or an imminent deadline, and do not run Smart Send Time tests around major dates or dates that matter to your brand. The exploratory email should be broad and non-urgent, like a weekly newsletter, and the page suggests turning off Smart Sending so that the same people all have the chance to open. In our view, exploration therefore belongs in October, on regular newsletters, so that you reach BFCM with an optimal time already known.

A few useful points from the FAQ: you cannot run an A/B test on Smart Send Time emails, because only one parameter should vary at a time. The model waits for the end of the conversion period before recording results, and that period is 5 days by default. A campaign can be excluded from the analysis if it contains invalid data, for example a tiny audience or discrepancies caused by Smart Sending. Finally, the page distinguishes Smart Send Time, which looks for the best time, from Smart Sending, which limits the number of emails received: our article on Smart Sending covers the latter.

Personalized Send Time: one time per recipient

Personalized Send Time schedules each message at the time predicted to be best for each recipient, within a delivery window that you choose (Klaviyo, Personalized Send Time). Unlike Smart Send Time, which finds a single time for the whole audience, it optimizes at the profile level.

Conditions and limits noted on the page:

• It is reserved for Marketing Analytics or Advanced KDP plans, which are not part of the standard marketing app and require a subscription.
• It covers email, SMS, push and WhatsApp campaigns, and does not yet cover flows.
• Scheduling happens at least one day ahead: no same-day sends.
• A content A/B test is possible if the test size is set to 100%.
• For SMS, it respects quiet hours, so the window is narrower.

The page advises against this tool for time-sensitive content, such as flash sales, expiring offers or urgent announcements that must reach everyone before a specific time. It recommends leaving a moderate gap between two campaigns with overlapping audiences, because recipients receive at different times and Smart Sending can skip messages that are too close together.

To measure the effect, Klaviyo keeps a randomly chosen control group, which receives the same campaign on a non-personalized schedule (the account's historical time, or a fixed time in the recipient's time zone). The results compare the two groups on opens, clicks and orders, and appear after at least 48 hours. The open and click rates in these reports exclude bot activity, including Apple Mail Privacy Protection opens, so they can differ from the rates shown elsewhere.

Which strategy for which BFCM send

This table is Deliver advice, based on the limits described above.

The BFCM send calendar gives the day-by-day sequencing, and our article on the best time to send an email details how to read time slots.

Checklist before BFCM

These points are Deliver advice.

1. Every campaign on the calendar has a send strategy decided in advance: fixed, gradual or local time zone.
2. Offers that end at a precise hour use a specific time zone.
3. The Determine recipients at send time option is turned on or off on purpose, and its behavior with local time zone sending is checked in your account.
4. Personalized Send Time, if available, is scheduled at least one day ahead, with a gap between campaigns that share audiences.
5. No Smart Send Time test is launched during Black Friday week.
6. An off-peak minute value is entered for the most important fixed-time sends.

FAQ

Is Smart Send Time available for every store?

No. Exploratory and targeted sends require at least 12,000 recipients, and the tool exists for email only.

Can you use Personalized Send Time for a same-day send?

No. Scheduling must happen at least one day ahead.

Can you use Personalized Send Time in a flow?

Not for now: the page says it is not yet available in flows.

What happens if the time has already passed in a recipient's time zone?

You choose: send immediately, or wait for the same time the next day. With immediate sending, the time can no longer be changed after scheduling.

Can you run an A/B test with Smart Send Time?

No. Only one parameter should vary at a time, so an A/B test is not possible on Smart Send Time emails.

Want an outside look at your send plan? We run Q4 readiness audits, or you can talk directly with the Deliver team.