Message formatting and limits

Every message you send through Blue Reacher delivers on one of two channels: imessage, or sms when the recipient cannot take a blue bubble. The two do not accept the same content. This page tells you what each one carries, what gets rewritten on the way down, and what to build so a single payload works on both. (RCS columns below are ecosystem reference for recipients whose devices render rich SMS; the platform's own fallback is SMS.)

Text

Message text goes in the content field as UTF-8. Whitespace is preserved, including line breaks (\n). There is no markdown rendering on any channel. Asterisks stay asterisks.

Length caps

Caps are not targets. For a first touch on a cold thread, stay between 90 and 320 characters. Past roughly 400 characters an iMessage bubble stops fitting on one screen, and reply rates on multi-screen opening messages drop hard. Save the long version for the reply.

SMS segment math

SMS is the only channel where character count costs money. The encoding your text triggers decides how many characters fit per segment.

One curly apostrophe pasted from a doc editor cuts your SMS capacity by more than half. Strip smart punctuation before you send: replace curly quotes with straight quotes, the ellipsis character with three periods, and long dash characters with a comma or a period. In GSM-7, the characters ^ { } [ ] ~ \ | and the euro sign each count as two.

Emoji

iMessage and RCS render the full current Unicode emoji set, including skin tone and multi-person sequences. SMS renders whatever the receiving handset supports, so emoji added after roughly 2021 can land as an empty box on older Android devices.

Two rules that matter operationally:

• One emoji in an SMS-fallback message costs you 90 characters of capacity. Decide whether it earns that.
• A skin tone modifier or a family sequence is several code points, not one character. A single such emoji can consume 7 to 11 characters of your budget.

Emoji in the content field never affect iMessage deliverability. They affect SMS cost and SMS rendering only.

Media

Attach files with media_url. Blue Reacher fetches the file, stores a copy, and sends that copy. One media_url per message. To send several files, send several messages 2 to 4 seconds apart.

Your media_url must:

• Use HTTPS with a valid certificate
• Return HTTP 200 within 10 seconds, with no authentication challenge and no redirect chain longer than two hops
• Send an accurate Content-Type header (this is how the file type is detected, not the file extension)
• Stay reachable for at least 60 minutes after the request if it is a signed URL

Supported types and size limits

The practical target for anything you want to look identical on all three channels is an image under 500 KB. A 1200 x 1200 JPEG at quality 80 lands near 250 KB and fills the bubble on every device. Animated GIFs should stay under 3 MB.

For video, encode H.264 baseline profile with AAC audio, keep it under 30 seconds, and keep the file under 10 MB. That clears iMessage and RCS intact and keeps the SMS link small enough to load on a weak connection.

Voice memos

To render as a playable voice memo bubble on iMessage rather than a generic file attachment, send .caf or .m4a with mono audio at 22 kHz or lower. MP3 and WAV files attach as documents and lose the waveform and the inline play button.

Keep voice memos under 60 seconds. Anything past two minutes is usually not played. On RCS the same file arrives as an audio attachment with a plain play control. On SMS it becomes a link.

Links

A bare URL in content renders as a rich preview card on iMessage. The preview is built on the recipient's device from your page's Open Graph tags, not by Blue Reacher. For the card to appear you need og:title, og:description, and an og:image under 1 MB on a page that returns 200 to an anonymous request. If your page sits behind a bot filter or a cookie wall, the card fails and the recipient sees a plain blue link.

Put the URL on its own line at the end of the message. A URL in the middle of a sentence still previews, but the card pushes the rest of your copy down.

Why public URL shorteners hurt you

Do not send bit.ly, tinyurl.com, or any other shared shortener domain. Four concrete reasons:

1. Reputation is shared. Carrier SMS filters score the domain, not your account. Every spam campaign that used that shortener this month is part of your score.
2. Several public shortener domains are already on US carrier blocklists. The message is dropped silently and you are billed for it.
3. Each redirect hop is another chance for the preview fetch to time out. Two hops means the iMessage card usually fails to build.
4. Recipients cannot see the destination. A hidden destination in an unsolicited message reads as a scam, which drives the report rate that governs your line health.

Use a subdomain you control, like go.yourcompany.com, with a valid certificate and exactly one redirect. Send it on warm threads first. Never put a link in the first message of a cold thread.

What survives the fallback

When a recipient is not reachable on iMessage, the message steps down to SMS. Content is rewritten on the way. Assume the SMS version is what a fallback recipient will see and write the copy so it still works there.

Every Blue Reacher line is a dedicated iMessage line, managed for you, with no A2P registration required. The fallback channels carry the same content rules described above.

Sending media

curl -X POST https://api.bluereacher.com/v1/messages \
  -H "Authorization: Bearer brk_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155550199",
    "message": "Here is the 40 second walkthrough I mentioned.",
    "media_urls": ["https://cdn.yourcompany.com/clips/walkthrough.mp4"]
  }'

{
  "success": true,
  "message_id": "d_1788120411520_a8x2mv",
  "mode": "drip",
  "queued": true,
  "scheduled_for": "2026-08-31T10:02:41.520Z"
}

media_urls takes 1 to 10 public https:// URLs (max 2048 characters each), on either the drip or instant lane, and message becomes optional when media is present. Media is fetched after the request returns; watch the message.sent / message.failed webhooks or poll GET /v1/status/{id}.

Serve files over public HTTPS with no auth wall and a correct Content-Type header; an unreachable or non-media URL fails the send rather than delivering text as a partial result.