Rules
Part of Why no feed ordering is neutral: the constraints that force a feed
Feed algorithms compared across seven platforms and four structural questions
TikTok, Instagram, YouTube, X, LinkedIn, Facebook and Reddit rank on four structural questions about feed algorithms, and the answers explain creator reach.
Ask what "the algorithm" does and you get a rumor with a company name attached. Ask what kind of surface you are looking at, and the answer holds across companies and survives their updates. That frame carries this comparison of feed algorithms across seven platforms and four structural questions.
TikTok, Instagram, YouTube and X matter most to publishers and marketers. So do LinkedIn, Facebook and Reddit. Each one runs several ranking surfaces at once, and the surface decides behavior, not the logo.
Seven platforms
- TikTok
- YouTube
- X
What to take away
- TikTok, Instagram, YouTube and X each run more than one ranking surface. So do LinkedIn, Facebook and Reddit. The surface decides what gets seen.
- Four structural questions, query, graph, time and slot count, predict behavior better than any leaked ranking detail.
- Reach means a different number on every surface. A figure that looks strong on one is meaningless on another.
- Advice ported between platforms fails at a predictable rate, because it was tuned to a structure the new surface does not have.
- Measure one number per surface. When one moves and the others hold, you have located the change.
Four structural questions
Ask these about the surface in front of you before anything else.
Four questions per surface
Is there a query?
matching dominates
prediction from behavior dominates
- Is there a query?A search box knows what the person wants. A feed has to guess. With a query, matching dominates; without one, prediction from behavior dominates. YouTube Search and Reddit Search carry a query. TikTok's For You does not.
- Is there a graph?Some surfaces show only sources the person chose. Others draw from everything. A graph bounds the candidate pool and changes what "new" means. X's Following tab and your LinkedIn connections are graphs. Instagram Explore is not.
- Does time matter?A stale surface is worthless. Others happily surface something from years ago. Where time matters, recency is a hard input. Reddit's Home feed and X move on in hours; YouTube Search will surface a five-year-old video.
- How many slots?A single slot is a decision. A short tray is a selection. An endless scroll is a ranking. Fewer slots means less room for exploration. TikTok's For You is endless; the Instagram Stories tray is a short tray.
Seven platforms compared on query, graph, time and slots
Seven platforms compared
Surfaces it runs
- TikTok
- For You, Following, Search, notifications
- Reels (up to 3 minutes), Feed, Explore, Stories tray
- YouTube
- Shorts (up to 3 minutes), Home, Search, Subscriptions
- X
- For You, Following, Search, replies
- Feed, Search, notifications, groups
- Feed, Reels (up to 90 seconds), Groups, Marketplace
- Home, Popular, subreddit feeds, Search
What it has to infer
- TikTok
- What a stranger will watch to the end
- Which of your followers opens now
- YouTube
- Whether a viewer stays past the first seconds
- X
- Which post earns a reply or a repost
- Whether a post reaches past your connections
- Which chosen source to show first
- Whether a post survives each subreddit's rules
What "reach" means there
- TikTok
- Views outside your follower base, which no TikTok dashboard splits out, so read it as views minus followers
- Reels retention plus the non-follower view share Instagram Insights reports
- YouTube
- Watch time, not impressions, visible as average view duration in YouTube Studio
- X
- Impressions against follower count, from your own post analytics on a 280-character free account
- Impressions and members reached on a post capped at 3,000 characters
- Share of followers reached in Page Insights
- Upvotes before the feed moves on, on posts whose titles cap at 300 characters
Look down the "infer" column. TikTok's For You and Instagram's Explore must infer the most, which is where behavior evidence dominates and where the two families of evidence a recommender uses matter most.
YouTube Shorts and Instagram Reels infer least about who you are; they read retention, and retention is a watch-time signal you can check in your own analytics.
Search is its own world on every one of them. With a query, the job is closer to classic retrieval, trading off precision and recall over items that can be matched to words. Search advice is advice about matching. It does not transfer to a feed, where nothing was typed.
Why the same post behaves differently
Publish one item and it enters several surfaces at once, and does differently on each. Each surface asks a different question of it.
- On X's Following tab, it competes only with accounts that person chose. The question is whether it beats them for a moment of attention.
- On TikTok's For You, it competes with everything. Early watch evidence decides, which is why the constraints that force a feed into stages bite hardest here: a cheap first pass has to find it before anything else can.
- On YouTube Search, it competes with everything matching the words. Whether it is any good matters less than whether it is findable.
- On Instagram's Stories tray, it competes with a handful of close accounts. Relationship dominates.
A following feed's value depends on the graph existing, which is a network effect: it is worth more to each person the more of their chosen sources are there. TikTok's For You has no such dependence, which is why it can be bootstrapped faster and why platforms push it.
Measuring per platform
The mistake is one reach number for everything. Instead, one number per surface, defined by that platform's row above.
- Instagram Reelsretention at three seconds, plus the fraction of views from non-followers, both in Instagram Insights.
- YouTube Shortsaverage view duration against your own median in YouTube Studio, not against a published threshold.
- LinkedInimpressions divided by connection count, pulled from post analytics before the window closes.
- TikTokviews against your follower count, and how that gap moved over the item's life.
- Redditupvote-to-view ratio in the first hour, per subreddit.
When one of these moves and the others hold, you have located the change to a surface, and the number of possible explanations drops sharply. The next question is which producer of evidence could have moved, asked about that surface alone.
Common questions
Is TikTok's For You just a following feed with the graph removed?
Structurally, close to it, and that removal changes everything. Without the graph the candidate pool is unbounded, so the cheap first pass matters far more, and early watch evidence becomes the main way anything gets found.
Why does search advice keep failing on feeds?
Because search has a query and feeds do not. Matching words to items is a different task from predicting response, and tactics for the first have nothing to act on in the second. It shows up on YouTube Search, where a video can rank for a phrase and still die on Home.
Which platform should I prioritize?
The one whose reach definition matches what you want. Followers who see you, strangers who find you, or people who search for what you do are three different goals. LinkedIn and Facebook lean toward followers who already chose you. TikTok's For You leans toward strangers. YouTube Search and Reddit Search lean toward people hunting a phrase.
Do the seven platforms change?
Products add, merge and remove surfaces all the time. The four structural questions do not change. When a new surface appears, answer the four questions and it will behave like whichever row it resembles. Track the appearances in your own change register.
