How long should a LinkedIn DM be? An evidence review

By Priya Nair, Data & Trends. Last updated: 2026-08-06

Most LinkedIn DM length advice is opinion dressed as data. A rep hears "keep it short" from a podcast and writes three-word openers that give the recipient nothing to reply to. Another hears "be thorough" and sends a paragraph that reads like a BDR wrote it (because one did). Neither approach is grounded in actual measurements.

A few things reps actually run into when researching this:

• They confuse the character limit on a connection request (tight, and different by plan) with the limit on a 1st-degree direct message (extremely generous, not the constraint they think it is).
• They apply LinkedIn post-length advice to DMs, which is a different mechanic entirely.
• They find conflicting advice and cannot tell which numbers come from real studies.

This piece is the honest evidence review. It separates what is measured from what is extrapolated, names sources, and is upfront about the biggest gap: no vendor, Reachium included, credibly publishes a DM-length-versus-reply-rate experiment, so the reader can weight each finding correctly.

What is the actual character limit on a LinkedIn connection request note?

The limit is tighter than most reps assume, and it differs by plan.

Free LinkedIn accounts can send personalized connection request notes of up to 200 characters, but LinkedIn caps free users at five personalized invitations per month. After those five, additional requests go out without a note. Premium and Sales Navigator users get a 300-character limit and no monthly cap on personalized invites, per LinkedIn's Help Center.

Practically: at 200-300 characters, a connection note is roughly two to three short sentences. That is the entire writing surface for a cold first touch on the standard connection path.

The connection request note strategy post covers what to put inside those characters. The limit question tells you the container; the note strategy tells you how to fill it efficiently.

What does LinkedIn's own data say about message length and reply rate?

LinkedIn publishes response-rate data from millions of InMail messages sent by corporate recruiters. The headline finding: InMails under 400 characters have a response rate 22% higher than the platform average. InMails over 1,200 characters land 11% below the average response rate.

The gradient matters. LinkedIn's data shows messages up to 800 characters still receive above-average response rates (+5%). Once you cross 800 characters, you are working against the average, not with it.

The directional finding is consistent: shorter messages outperform longer ones on cold first touches. The explanation LinkedIn offers is behavioral. Fewer than 10% of all InMails are under 400 characters, so brief messages are rare enough to stand out. A cold message at 200-350 characters reads as considered; a cold message at 1,000+ characters reads as copied-and-pasted.

Source: LinkedIn Talent Blog, InMail best practices.

Is there any first-party platform data on DM length?

No credible published study isolates DM length against reply rate, and it is worth understanding why. Message length is heavily confounded in real platform data: who sends long messages differs systematically from who sends short ones (different industries, different offers, different seniority of sender), so a raw length-versus-reply split measures the senders, not the length. Any vendor quoting an "ideal DM length" percentage without a named methodology is marketing, not measurement.

The nearest adjacent first-party finding is about presence, not length. Reachium's published connection-notes study found that among accepted connections, 47.80% replied when the request carried a note versus 25.54% without one (the study's acceptance-side result is inconclusive: the pooled gap reverses in the paired within-account test, so it makes no claim that notes help or hurt acceptance). The takeaway for the length question: writing something specific enough to seed a conversation is what the data rewards. The note's job is context, and 200-300 characters is enough room to do that job.

Post length is a different mechanic entirely: a post competes with every other piece of content in a feed for a three-second scroll decision, while a DM lands in a dedicated inbox. For that separate question, see ideal LinkedIn post length, which covers the algorithm mechanics that make post length matter differently from DM length.

What is the character limit on LinkedIn InMail and direct messages?

The limits vary by message type:

The practical implication: the character limit is a constraint only on the connection request note. Once someone is a 1st-degree connection, the technical limit on a direct message is high enough that the question shifts from "what is the limit?" to "what does the reader actually want to read?" The answer to that question, per LinkedIn's InMail data, is still: shorter.

Source: LinkedIn Help, InMail character limits.

Why do short messages outperform on cold outbound?

Three mechanisms, each independently verified:

Mobile consumption. Most LinkedIn notifications are opened on mobile. The preview text shown in a push notification or inbox view is roughly 50-100 characters. A 400-character message fills the preview and invites a tap; a 1,500-character message buries the ask below a fold the recipient may never reach.

Pattern recognition. Long cold messages pattern-match to automation. Recipients who receive dozens of cold outbound messages per week have calibrated quickly: a message that fills the preview and continues below the fold was not written for them specifically.

The one-reason principle. A 200-300 character message can carry one clear reason to reply: a specific trigger, a shared connection, a pointed question. A 1,000-character message usually carries two or three reasons stacked, which dilutes intent. The recipient cannot identify the ask and defaults to ignoring the message rather than parsing it.

This is the same logic behind the outreach-templates-40-percent-reply-rate framework: one specific reason, one specific ask, nothing extra.

When does a longer LinkedIn message actually work?

The sub-400-character rule is specifically for cold first touches. Context shifts the calculus in several situations:

Warm follow-up after a reply. Once someone has responded, the conversation is no longer cold. A longer, more detailed message is appropriate because the recipient has signaled they are engaged. Length is no longer an attention tax; it is information delivery.

Recruiter outreach where role detail is essential. Recruiter InMails addressing a specific role need enough detail to help the candidate self-select. Vague short InMails on a role produce low-quality replies or no reply at all. LinkedIn's recruiter data carves out this use case.

Tailored resource shares with real context. If you are sending a specific resource that is genuinely relevant to the recipient's situation, explaining why it matters in 500-600 characters is more effective than a three-sentence tease that leaves them unsure whether to click.

InMail subject plus short body. A structured InMail where the subject line carries the hook (under 50 characters) and the body delivers one pointed question (under 400 characters) is still short in total but uses both fields. This is the format that consistently scores highest in LinkedIn's InMail data.

How does Reachium handle message length in its Outreach campaigns?

Reachium's Outreach campaign type supports any sequence step length. The AI Personalization feature generates first lines, typically in the 80-150 character range, and the template body is set by the operator. Reachium's in-product editorial guidance leans toward the 200-300 character range for cold first touches on connection request notes, which aligns with both the character limits for free and Premium accounts and the direction of LinkedIn's reply-rate data.

The practical implication for reps scaling outreach: AI Personalization handles the first line within the right length window. The template body needs one deliberate edit, keeping the total under 400 characters for cold touches. See personalize-linkedin-outreach-at-scale for how to set up the personalization layer without losing volume.

What this evidence does not include: a published Reachium experiment comparing DM-length variants against measured reply-rate outcomes. Reachium's published research covers the acceptance and reply funnel, sending volume, connection notes, and timing, not message length. For the forward-looking picture of where outreach benchmarks are heading, see LinkedIn 2027 predictions.

FAQ

Does adding the recipient's name to a LinkedIn message make a longer message worth it?

No. Personalization improves reply rates, but it does not neutralize the length tax. A 1,000-character message that opens with "Hi [Name], I noticed you recently..." is still a 1,000-character message. The name buys goodwill on the first line; it does not earn the recipient's attention for paragraphs three and four. Keep the length short and use the personalization within that budget, not as a reason to expand it.

Is voice note or video DM length measured the same way?

No. Character limits apply to text. Video and voice notes are measured in time (up to 10 minutes for video DMs). The same attention principles apply directionally: a 90-second voice note is more likely to be played than a seven-minute one, and a video DM that gets to the ask within 30-40 seconds outperforms one with a two-minute preamble. The underlying mechanism is identical (respect the recipient's decision window) even though the unit differs.

Should I send a long connection request note and then shorter follow-up messages?

The opposite approach works better. Send a short note on the connection request (under 200 characters for free, under 300 for Premium), then a short follow-up DM once connected (under 400 characters). Reserve longer messages for after you have received a reply and established that the recipient is engaged. Starting long signals automation before it signals thought. Worth knowing when weighing the effort: Reachium's published notes study found the reply payoff of a note is large (47.80% vs 25.54% of accepted connections replying), while its acceptance-side effect is inconclusive.

How long should a LinkedIn InMail subject line be?

LinkedIn's character limit on InMail subject lines is 200 characters, but best-practice guidance from LinkedIn's Talent Blog puts the effective limit much lower: under 50 characters, because most inbox views and push notifications truncate the subject at that point. A subject line that is cut off mid-word on mobile is worse than a short, complete one. The subject should carry the hook in full; treat any character over 50 as likely invisible.

Does LinkedIn message length affect deliverability or just reply rate?

Message length does not affect whether a message is delivered. LinkedIn's platform delivers messages regardless of length (within limits). Length affects reply rate through behavioral mechanics, not technical filtering. The one relevant deliverability factor is that messages flagged as spam by recipients can reduce your account's message-sending ability over time. Shorter, more relevant messages produce fewer spam flags, which is an indirect deliverability effect but not a direct one.

Sources

• LinkedIn Talent Blog: These InMails Get the Best Response Rates
• LinkedIn Help: InMail character limits
• LinkedIn Help: Personalize invitations to connect
• Reachium Research: Do connection notes work?
• Reachium: reachium.io
• Linked Insider: LinkedIn outreach benchmarks 2026