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What the Facebook Algorithm Actually Measures — The 4 Core Signals

Most articles about the Facebook algorithm list dozens of ‘ranking factors’ without a hierarchy. The truth is simpler: the algorithm measures four core signals, and everything else is a refinement on top of those four. This guide breaks down what each signal actually measures, how they combine into a single ranking score, and which signals you can influence versus which are structural.

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What You’ll Learn

  • The Facebook Feed algorithm reduces to 4 core ranking signals plus secondary refinements
  • Signal 1 — Relationship: viewer’s interaction history with the source account (2–3× boost when recent)
  • Signal 2 — Content type preference: viewer’s historical format engagement (per-viewer, not per-page)
  • Signal 3 — Post performance: engagement velocity in the first 90 minutes
  • Signal 4 — Recency: half-life decay of roughly 50% every 6 hours
  • Two signals are controllable (format choice + posting time), two require time to influence (relationship + page-level history)

The Four Signals That Decide Everything

Strip away the dozens of “ranking factors” articles you’ve seen and the Facebook Feed algorithm reduces to four primary inputs. Every other ranking factor mentioned in industry articles — content authenticity, integrity classifiers, format-specific quality scores — is a refinement layered on top of these four.

SMMNut’s Facebook Algorithm Signal Breakdown identifies 4 core inputs to the Feed ranking score: (1) Relationship Signal — how frequently the viewer has liked, commented on, or shared content from this source. Accounts with recent interactions receive a 2–3× boost to all subsequent content visibility. (2) Content Type Preference — Facebook tracks which formats each user engages with most and prioritises similar formats. A user who consistently watches Reels receives more Reels in their Feed regardless of source.

Signal 1 — Relationship Strength

The relationship signal measures the rolling interaction history between viewer V and source S across all interaction types: reactions, comments, shares, profile visits, message thread depth, tag interactions, story views. Facebook computes this as a weighted decay model — recent interactions weigh heavily, older interactions decay quickly.

What “Strong Relationship” Looks Like

  • Viewer V reacted to the most recent post from source S within 72 hours
  • V has commented on 3+ posts from S in the last 30 days
  • V has clicked into S’s profile in the last 14 days
  • V messages S or has been messaged by S in the last 30 days

A viewer meeting 2+ of these criteria for your Page receives a 2–3× ranking boost for your next post compared to a viewer who follows you but has no recent interaction history.

Why This Matters

The relationship signal is why “engagement bait” pages collapse over time. Engagement bait drives reactions but not the deeper interactions (comments, profile visits, repeated interaction over weeks) that build relationship strength. The relationship signal also explains why DM replies and comment replies have outsized long-term value — they build relationship strength on a per-follower basis that compounds with every future post.

Signal 2 — Content Type Preference

Facebook segments every viewer’s engagement history by content format: Reels, Feed videos, image carousels, single images, text status, link posts, polls, events. The viewer gets a per-format affinity score updated continuously.

When the algorithm scores candidate posts for that viewer, it heavily weights format affinity. A viewer with high Reels affinity sees more Reels regardless of which source posted them. A viewer with high carousel affinity sees more carousels. This is per-viewer ranking — the same Reel can be #1 in one viewer’s Feed and not appear at all in another viewer’s Feed, based on format preference alone.

What You Control

You don’t directly control your viewers’ format affinities — those are built by their own consumption history across the platform. What you control is matching format to where your audience already engages. If your Page Insights show that your audience overwhelmingly engages with Reels, posting carousels is leaving distribution on the table.

Signal 3 — Post Performance Signals

(3) Post Performance Signals — the content is evaluated on engagement velocity (interactions per hour in the first 90 minutes), engagement quality (comments and shares weighted higher than likes), and content authenticity signals (original content vs reshared content). (4) Recency Signal — content has a time-decay factor: posts lose approximately 50% of their distribution potential every 6 hours after publication. This is why timing and early engagement are critical for Facebook content performance.

The Engagement Velocity Threshold

Facebook’s 2026 ranker evaluates engagement accumulation in the first 90 minutes after publication. Posts that clear an engagement velocity threshold (engagement rate relative to early reach) get amplified into expanded distribution. Posts that don’t clear the threshold receive heavily reduced subsequent distribution — even if they accumulate substantial engagement later, the algorithm has already decided.

Engagement Quality Hierarchy

Engagement TypeApproximate WeightWhy
Share~5×Strongest signal: viewer found content valuable enough to broadcast
Long comment (10+ words)~3×Effort signal: viewer invested time
Save~3×Intent signal: viewer wants to return later
Short comment (≤9 words)~2×Active engagement but lower effort
Reaction (love, wow, haha, etc.)~1.5×Active but minimal engagement
Like1× (baseline)Lowest-friction engagement
View / impression0×Passive — not engagement

Content Authenticity

The 2026 algorithm adds an “original content” signal: content first published to Facebook (with original metadata) outranks the same content reshared from another platform. A native video upload outperforms the same video uploaded via cross-posting tools.

Signal 4 — Recency

Content has a half-life. Approximately every 6 hours after publication, a post loses 50% of its remaining distribution potential. By 24 hours, a post is at ~6% of peak distribution capability; by 48 hours, ~0.4%. This is why timing matters — and why posting times outside your audience’s active window can permanently cap a post’s reach even if the content is excellent.

Recency Is Not Punishment

The recency signal exists to keep the Feed feeling current. A 3-day-old post competing against a 1-hour-old post would feel jarring even if the older content was higher quality. The system favours fresh content as a UX choice, not as a penalty for the older post.

How the 4 Signals Combine

Each candidate post receives a ranking score that approximates:

Score = (Relationship × Format Affinity × Performance Signal × Recency) + Secondary Modifiers

The four primary signals multiply rather than add — meaning a single weak signal drags the entire score down. A post with strong relationship, strong format match, and good content but published 18 hours ago gets demolished in ranking by a post with the same first three signals published 1 hour ago. Conversely, a post published at the perfect time with terrible engagement velocity (signal 3) cannot be saved by good timing alone.

What You Can Influence vs What You Cannot

What marketers can influence vs what they cannot: Controllable — content type selection (to match format preference signals), posting time (to maximise recency signal impact), content quality (to drive early engagement velocity). Not directly controllable — relationship signal between viewer and page (must be built over time through consistent interaction), platform-level algorithm weights (Facebook adjusts these quarterly).

Direct Controls

  • Format choice — pick the format your audience’s affinity matches
  • Posting time — align with your audience’s active window for maximum recency × early engagement compounding
  • Content quality — drives the engagement velocity needed to clear the 90-minute threshold
  • Engagement triggers — opening lines, questions, hooks that drive shares and saves

Indirect Controls (Build Over Time)

  • Relationship strength — built by replying to comments and DMs, tagging engaged followers, consistent posting cadence
  • Page-level engagement rate baseline — improves over rolling 28-day windows as per-post engagement quality improves

Not Controllable

  • Platform-level algorithm weights (Facebook adjusts these quarterly)
  • Your followers’ format affinities (built by their cross-platform consumption history)
  • Competing content from your followers’ personal connections (always outranks Page content in their Feed)

The Practical Takeaway

If you only optimise for the four core signals, you will outperform Pages that try to game the dozens of “ranking factors” listed in industry articles. The mental model:

  1. Post in the format your audience engages with most (signal 2)
  2. Publish at the time your audience is most active (signal 4)
  3. Front-load engagement triggers in the opening 90 minutes (signal 3)
  4. Reply, comment, and engage with your audience to build relationship strength (signal 1)

For the deeper breakdown of how these signals manifest as observable ranking factors in your Page Insights, see Facebook Feed ranking factors explained. For how past engagement specifically feeds into future ranking, see Does past engagement affect future Facebook reach. And if you are diagnosing a reach drop in real time, start with Why your Facebook reach is dropping. The complete model lives in the Facebook algorithm complete guide.

FAQ

What does the Facebook algorithm actually look at?
Four core signals: (1) relationship strength between viewer and source, (2) the viewer’s format preference history, (3) post performance signals during the first 90 minutes, and (4) recency. These four combine multiplicatively into a single ranking score, with dozens of secondary modifiers refining the result.
Facebook scores each of your followers individually for each new post. Followers with strong relationship signal to your Page, format affinity matching your post’s format, and recent activity windows see your post first. If their early engagement clears the velocity threshold, distribution expands to lower-affinity followers.
Yes, more than most realise. The recency signal causes a post to lose roughly 50% of its remaining distribution potential every 6 hours. Posting when your audience is offline means the recency decay starts before they ever see the post — usually a permanent cap on reach for that post.
Yes — Reels currently have a 40% baseline distribution premium over Feed videos in 2026, and native video outranks link posts and text status by 30–60% at equivalent engagement rates. But the bigger factor is per-viewer format affinity: viewers see formats they engage with most, regardless of source.
Decisive. The 90-minute engagement velocity window determines whether a post gets amplified or capped permanently. Posts that don’t clear the threshold during those 90 minutes receive heavily reduced subsequent distribution even if they earn engagement later — the algorithm has already classified them.
Indirectly. Follower count is not a direct ranking input. But more followers means a larger pool of potential early-engagement candidates, increasing the chance of clearing the velocity threshold. A 50,000-follower Page with 4% engagement rate dramatically out-reaches a 10,000-follower Page with the same rate.
Not durably. Tactics that exploit a specific signal (engagement bait for Signal 3, mass-tag for Signal 1) trigger penalty classifiers that demote the entire Page for 30–60 days. The durable strategy is aligning with what each of the four signals is actually trying to measure — viewer satisfaction with your content.
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