Loop in is a separable phrasal verb for adding someone to an ongoing conversation, and separable phrasal verbs come with a grammar rule that isn't obvious from the words alone: with a pronoun object, the pronoun has to sit between "loop" and "in," never after it.
The most natural pattern is loop [someone] in on [a project/topic]. The most natural adjective form is keep [someone] looped in. The rule that catches people out: loop her in, not loop in her; loop them in, not loop in them.
Core pattern: object plus "in on"
With a name or full noun phrase as the object, "loop in" splits cleanly around it, and "on" introduces the topic they're being added to.
"I will make sure to loop the finance director in on the latest budget adjustments before the board meeting."
"Please loop Sarah in on the progress report so she can provide feedback."
That "in on" combination is doing two jobs at once -- "in" is the particle that completes the phrasal verb, and "on" attaches the specific subject matter. Drop "on" and name the topic some other way, and the sentence still works, but "in on" is the tightest, most idiomatic form.
Pronoun rule: it has to split
When the object is a pronoun instead of a name, the split isn't optional.
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Start learning for free →"Our client just requested a change in scope for the upcoming project. I need to get the account manager updated on the details; please loop him in before I send the reply."
"Loop him in" is correct. "Loop in him" is not, because separable phrasal verbs require a pronoun object to sit inside the verb-particle pair, not after it. The adjective form, "keep [someone] looped in," follows a different but equally fixed pattern -- "looped in" functions as a participle describing an ongoing state of inclusion.
What doesn't collocate
The first mistake is reaching for "into" instead of "in": "we need to loop into the manager for this final decision" isn't natural -- the fixed particle is "in," and the person goes right after the verb: "loop in the manager." The second mistake is the pronoun-placement error above in its noun-forwards direction -- "it is important to loop in them regarding the client's request" needs to become "loop them in," because a pronoun object can never follow the particle in this phrasal verb.
Practice scenarios
Practice using loop in in situations like:
- adding a stakeholder to an email thread so they can follow a project's progress
- asking a colleague to include someone on a decision before you send a reply
- correcting yourself mid-sentence when a pronoun object slips to the wrong side of "in"
Useful practice phrases:
- "Could you loop Maria in on this thread so she can follow along?"
- "Please loop him in before we send the reply -- not 'loop in him.'"
- "I'll loop in the legal team on the contract changes."