Show a Block to Only Some Readers

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A block’s condition decides who sees it — everyone, only readers on a certain kind of device, or only readers who belong to chosen audience segments. Everyone else simply doesn’t see that block; the rest of the newsletter reads normally around it.

That means you can run a wide banner for desktop readers and a compact version for phones using two blocks in the same send, or slip a members-only note, a local notice, or a tailored call to action into an edition without building and scheduling a second one — each reader sees only what’s meant for them.

Set a condition

This works on a standalone Image or Promotion block — one that isn’t nested inside a multi-column layout. Other block types, and any block nested in a layout, don’t have a CONDITIONS section at all (see Which blocks offer it below).

Open your newsletter and click the block you want to set a condition on.
In the settings panel, scroll to the CONDITIONS section.
If the block offers both kinds, choose Based on devices or Based on audiences from the Display based on dropdown. If it only offers one kind, that one appears directly with no dropdown to choose from.

Based on devices

Under Display conditions, choose one:

Display all the time — everyone sees the block. This is the default.
Display on desktop only — the block appears for readers on a computer and is hidden on phones.
Display on mobile only — the block appears for readers on a phone and is hidden on computers.

Based on audiences

Under Match audience, choose All or Any — whether a reader must match every segment you pick, or just one of them.
Under Segments, select one or more segments from the Custom group (segments you’ve built yourself — see User Tags and Segments) or the System group (Letterhead’s built-in engagement segments, like Loyalists or Ghosts).
Only readers matching your chosen segments (and match rule) see the block; everyone else gets the edition without it.

This mode works only when your newsletter sends through Letterhead’s own delivery — not a connected ESP like Iterable or Mailchimp — since resolving a condition per recipient requires Letterhead’s own send pipeline.

The choice saves with your newsletter like any other block setting, and you can change it any time before you send.

Which blocks offer it

Device conditions are available only on a standalone Image or Promotion block — one that isn’t nested inside a multi-column layout.

Audience conditions are available on most block types, including HTML blocks (which can’t offer a device condition) — everything except the Footer and the View in browser block, which always render for everyone since they carry no reader-specific content to gate. Like device conditions, a block nested inside a multi-column layout doesn’t offer an audience condition either.

Neither kind is offered on a Google Docs, Markdown, or Iterable snippet block.

Why an Iterable snippet block doesn’t offer one

If you send through Iterable, you’ll notice the snippet block has no CONDITIONS section — and it isn’t coming. It’s worth knowing why, because the reason is the same thing that makes snippets useful.

Your snippet’s HTML never passes through Letterhead. We send Iterable a placeholder in its place, and Iterable drops your stored HTML in at send time, after everything we build has already been finished and handed over. Every other block sits inside the responsive layout we wrap around it, and that layout is exactly what decides how a block behaves between a desktop screen and a phone.

So putting a device condition on a snippet would mean nesting your HTML inside ours at a stage neither of us can see, preview, or test. We can’t check the result against your templates, and we can’t predict how your styling and ours will get along once they’re combined in a real inbox. The likely outcomes are a layout that shifts between desktop and mobile, styling that fights itself, and a heavier email — and the first anyone would find out is after a live send to your audience, which is the worst possible place to learn it.

The dependable place to handle a per-device difference in a snippet is inside the snippet itself, where your own HTML is in charge and nothing of ours is wrapped around it.

Check it before you send

Both kinds of condition can be checked on the Preview and schedule step, without sending yourself a test.

Device conditions

Switch between the desktop and mobile views in the editor’s preview. A block set to mobile only disappears from the desktop view and comes back in the mobile view, and a desktop-only block does the opposite — so you can confirm each reader gets what you intended.

The switch between the two happens at your newsletter’s mobile width, the same setting that governs the rest of your mobile layout. See How do I use the new design settings? to check or change it.

Audience conditions

When your newsletter has at least one block with an audience condition, a Preview as control appears beside the desktop and mobile toggle at the top of the preview step. Use it to see the edition the way a particular kind of reader receives it:

Click Preview as. The segments your blocks are conditioned on are listed first, under In this newsletter, with the rest of your segments below them. Search if the list is long.
Tick one or more segments. A reader can belong to several at once, so tick every segment the reader you have in mind would be in — a block set to match All of its segments only appears when you have ticked all of them.
The preview updates as you tick. A block that reader wouldn’t receive is replaced by a short amber note saying it is hidden for this audience, so you can tell a hidden block from one you never added.

All subscribers, the starting choice, previews the edition for a reader who isn’t in any of your segments. That is the version most of your audience receives, so any block limited to a segment is hidden there — which is usually the quickest way to confirm the condition is set at all.

Two things this preview can’t show you:

Tag-based conditions are matched against each reader at send time, so the preview always shows those blocks.
Conditions your ESP resolves — such as a Braze reader attribute — are applied by that service as it sends, so the preview shows the block unchanged.

Good to know

A few email apps always show the desktop version. Some older desktop email programs — Outlook on Windows is the common one — can’t tell how wide the screen is, so they show what a desktop reader would see. A desktop-only block appears there, and a mobile-only block stays hidden. Keep anything essential in a block that displays all the time.
Hiding a block doesn’t make your email smaller. A hidden block is still delivered, it’s just not shown, so it still counts toward your email’s weight. Use display conditions to tailor what a reader sees, not to trim a newsletter that’s getting heavy.
Don’t hide something a reader needs. If a link, an offer, or a piece of housekeeping matters to everyone, leave it on Display all the time rather than trusting every email app to get the switch right.

Next steps

Adjust mobile font size and padding to tune how a block reads on phones without hiding it.
Set up promotions to create the ad placements you can then tailor per device.

Still can’t find what you need? Contact support.