Send LinkedIn Voice Notes and Videos From Your Campaigns

Learning objective

By the end of this article, you'll know how to attach a voice note, a video or a PDF to a LinkedIn message step, which file formats LinkedIn accepts, and how to recognize and fix the one format problem that made voice notes disappear for some users.

Why this matters

A voice note adds tone and personality that text can't. Prospects hear a real person, and reply rates go up on first-touch messages. A short video does the same for product context.

Media only helps if it actually arrives. Earlier this month a customer showed us a voice note that played perfectly inside Outly but never reached a single prospect. The cause was a file format LinkedIn refuses. This article gives you the working setup and the formats we verified directly against LinkedIn.

Prerequisites

• An Outly account with a connected LinkedIn profile.
• A campaign with at least one LinkedIn message step (Starter or follow-up).
• A microphone or camera in your browser, or a pre-recorded file in one of the supported formats below.

Core lesson: step-by-step workflow

Phase 1: Open the message step

1. Open your campaign and go to the Workflow tab.
2. Select the LinkedIn message step you want to enrich, for example Starter (Linkedin).
3. Scroll to Media attachments. You'll see three slots: Voice notes, Videos and PDFs.

Every file attached here is sent when the step runs. You can attach several files of each type, and all of them are sent. Each team member uses their own media. Without an upload, the message is sent text-only.

Phase 2: Add a voice note

1. In the Voice notes slot, fill in Describe this file. This label is for you and your team.
2. Fill in What should the AI know about this media? Outly uses it when writing the message text, so the text and the audio fit together.
3. Choose how you want to add the audio:
   • Record in the browser by clicking Record, speaking, then Stop and Save.
   • Upload a pre-recorded file.

Voice note rules

• Supported file type: .m4a, .mp3, .wav, .ogg, .flac, .aac, .wma
• Not supported: .webm
• Max duration: 1 minute
• Max size: 20MB

When you record in Outly, the browser produces an M4A file, or an OGG file in browsers that cannot record M4A. If your browser can do neither, the Record button is hidden and you'll be asked to upload a file instead.

Phase 3: Add a video

1. In the Videos slot, fill in the label and the description the same way.
2. Click Record for an in-browser recording, or Upload a file.

Video rules

• Accepted formats: MP4 or MOV
• Not supported: .webm, .avi, .3gp
• Max size: 20MB per video

Phase 4: Review and launch

1. Save the step.
2. Check the 1 file counter at the top right of the step, which confirms the attachment is stored.
3. Launch the campaign, or approve the drafted messages in Messages if your campaign uses review before sending.

How Outly sends media on LinkedIn

Outly sends the text message first. Then it sends each voice note as its own message, because LinkedIn treats every voice note as a separate message. Videos and PDFs travel as attachments of the text message.

If LinkedIn refuses an attachment, the text message is still delivered and nothing is sent twice. The refusal is written to our logs and the campaign moves on to the next contact. Your prospect always gets the message, with or without the media.

Practical application: what we found in the logs

The customer's recording was a .webm file, the default format that Chromium browsers produce when you record audio. Our logs showed the same line after every approved message in his campaign:

Voice note failed; main message already delivered
error: The media has been rejected by the provider.

Forty sends, forty refusals, always the same file. The messaging provider returns HTTP 415, Unsupported Media Type, for WebM voice notes, and its documentation names M4A as the preferred format for LinkedIn.

Documentation says "prefer". We wanted "accepted". So we took one 7.5-second recording, encoded it in every common audio container, and sent each one as a voice note from one of our LinkedIn accounts to another.

Format	Result
.m4a (AAC)	Delivered as a voice note
.mp3	Delivered as a voice note
.wav	Delivered as a voice note
.ogg (Opus or Vorbis)	Delivered as a voice note
.flac	Delivered as a voice note
.aac	Delivered as a voice note
.wma	Delivered as a voice note
.webm (Opus)	Refused, HTTP 415

Ogg with the Opus codec passed. WebM with the same Opus codec failed. The container is the problem, not the audio encoding.

We ran the same test for video: MP4 and MOV are documented and passed, WebM and MKV passed the API too, AVI and 3GP were refused. We kept the documented pair, MP4 and MOV.

Best practices

• Keep voice notes under 30 seconds for cold outreach. Say who you are, why this person, and one question.
• Record in a quiet room and check the microphone dropdown before you start.
• Write the media description as if briefing a colleague. The AI uses it to keep the text consistent with what you say.
• One voice note per step is plenty. Several voice notes in a row feel like spam.

Troubleshooting and pitfalls

Issue: my voice note plays in Outly but prospects never receive it

• Root cause: the file is a .webm recording made before this change, which LinkedIn refuses.
• Fix: remove it from the step and record it again in Outly, or upload an .m4a or .mp3 version. New recordings are never WebM. Existing WebM recordings are being converted on our side, and the accounts concerned are being contacted.

Issue: the upload is refused

• Root cause: the file type is not in the supported list, or it exceeds 20MB or 1 minute.
• Fix: export the audio as .m4a or .mp3, or the video as MP4 or MOV, and compress it below 20MB.

Issue: the Record button is missing

• Root cause: your browser cannot record in a format LinkedIn accepts.
• Fix: record with another app and upload the file, or use a Chromium-based browser or Safari.

Issue: the video won't upload

• Root cause: the file is .avi, .3gp or .webm.
• Fix: convert it to MP4 (H.264 video, AAC audio), which every LinkedIn client plays.

Related articles

• Set up a LinkedIn campaign workflow in Outly
• Review and approve drafted messages before sending