What X's own ranking code says about replies

X keeps the code that ranks the For You feed in a public repository. Most posts about "the algorithm" quote each other. These figures come from the repository itself, as it stood at the end of September 2026.

The weights

For every post it might show you, the system predicts how likely you are to do various things with it. Each prediction is multiplied by a weight, and the results are added into a score. Some of the weights:

There is also a boost of 15.0 that applies when you and the author follow each other.

What the weights don't mean

You will see claims like "one reply is worth ten likes". That's a misreading, and X says so in the repository. The weights multiply a predicted probability, not a count. A post doesn't earn 5 points when someone replies. It scores higher for a viewer when the model thinks that viewer is likely to reply.

The honest summary: X wants to show people posts they will talk under, and wants very badly not to show them posts they would report.

The filter nobody mentions

The code includes a filter that removes replies from accounts you don't follow from your For You feed. So when you reply under a stranger's post, that reply does not travel into their followers' feeds as a post of its own.

Your reply's audience is the people who open that thread. That is still a lot of people when the thread is under a post that's taking off, which is the whole reason to pick threads carefully.

What a small account can take from this

• Reply where threads are being read. A fresh post that's climbing has people opening it right now. A three-day-old post with a million views mostly doesn't.
• Start conversations, not applause. The system rewards posts people answer. A reply that invites an answer helps the thread and you.
• Mutuals matter. The mutual-follow boost is the biggest positive number in that table. Every person who follows you back is a small permanent advantage.
• Never be reportable. One predicted report outweighs hundreds of predicted likes. Spammy, off-topic or pushy replies cost more than silence.

The code changes. Weights can be retuned without an announcement, and the repository shows the For You feed, not how replies are sorted inside a thread. Nobody outside X has measured that.