Prominently showing the rules or norms of a platform or online group, either as people are entering an online space for the first time or as a reminder when they revisit that space.

This design solution has many variations, some more effective than others. Rather than review each variation, we consider three broad categories that are based on two salient dimensions: who sets the rules or norms and whether or not they are enforced.

Those categories are: 

• Community Norms & Rules: Norms set or used by a community that may or may not be enforced.
• Platform Rules. Norms set and enforced by a platform.
• Civility Prompts. Norms set by a platform, but not enforced.

Because norms are mostly effective when they are created or used within a community, we categorize and consider all rules and norms that are used by an online group as one category - "Community Rules & Norms" - whether or not they are enforced. 

In contrast, because a platform rarely operates as a community (small niche platforms may be exceptions), platforms can either display "Platform Rules", if they are explicitly enforced, or what we term "Civility Prompts" if they are unenforced. Rules are clear directions about what behavior is and is not acceptable, with platform enforced consequences if they are broken. Civility prompts are guidelines about how to behave with no indication that they will be enforced.

By reminding and making salient the rules or norms of a platform or online group, people will be more likely to engage prosocially by adhering to those rules and norms. In the case of community rules and norms, people naturally tend to behave in ways they know are acceptable within a community, and are more likely to do so when those norms are clear. In the case of platform rules, they will be more likely to follow rules - and avoid negative repercussions - if likewise they know what those rules are and that they are enforced. Civility prompts might work more subtly by either reminding people of general societal norms or priming one’s “better angels.”

We currently see reminders of Community Rules & Norms as a validated approach to increasing positive behaviors. Similarly, we see convincing evidence of the effectiveness of reminding users of Platform Rules. There is mixed evidence, however, that Civility Prompts are effective in increasing positive behaviors.

Community Rules & Norms

J. Nathan Matias (2019) conducted a large-scale field experiment on the Reddit sub (community) r/science, in which randomly assigned posts included a reminder of the subreddit's rules and a mention of how those rules are enforced. Posts that received the intervention were 8% more likely to have comments from new users comply with the community’s rules. At the same time the rules reminder increased the likelihood new users would comment on the thread by 70%. (Note: all effects we include are statistically significant, unless otherwise stated.)

It’s worth noting that the community rules for r/science were unusually strict (for example, during the course of the study, no personal anecdotes were allowed) and deviation from them by newcomers was previously unusually high.

In a related study conducted in collaboration with Nextdoor, 312 new groups were randomly assigned either to present users "group guidelines" before they joined the group or to present no guidelines. Groups with guidelines had significantly fewer comments reported for abuse (0.3% compared to 0.7%), providing more evidence that posting community norms discourages toxic behavior. (Kim et al, 2022)

Platform Rules

Tyler et al. (2021) ran a large-scale field experiment on Facebook in which people whose content was removed for breaking a platform rule were subsequently reminded in their feed either of that specific rule or, more generally, that rules are enforced. Compared to a control group of people who similarly had their content removed but who did not receive reminders, those who received reminders were less likely to re-offend.

Civility Prompts

While no existing public studies (to our knowledge) test Civility Prompts in a field experiment like the three above, we know that platforms use variations of prompts that proactively remind people to be considerate in their comments (see, e.g. Nextdoor’s Kindness Reminders). There are, additionally, two studies that test civility prompts in settings that either mimic or make use of online platforms - and which present mixed findings. 

Celadin et al. (2024) presented participants with a series of Facebook-like posts that they could engage with (like, comment on, etc.) after being presented with prompts that asked them to “take into account” either what they “believe others would do” or “believe others would approve or disapprove of” when making their decisions. In both cases, when compared to a control group that did not receive a prompt, those participants were more likely to interact with posts that were inoffensive than with harmful posts, an indication that the prompt results in more prosocial engagement. 

A second study (Oswald et al., 2025) invited participants to participate in one six of subreddits created for the study. In two of the subreddits, participants were given the following prompt before entering: "Please stay civil, respectful and on topic when discussing the political issues of the day. Avoid harassment, discrimination and offensive language." Counter to what the researchers expected, participants in the two subreddits that received that prompt were more toxic in their posts.There are several reasons this finding could be misleading, however, including:  baseline levels of toxicity were low compared to average subreddits, and participants interacted with each other in their conditions (which is not customary in experiments). Nonetheless, the researchers observe that increases in toxicity were mostly among a small set of participants who are more politically interested, suggesting that a civility prompt could backfire among certain users.

In sum, we find strong evidence that setting and reminding people of (enforced) platform rules and (enforced or unenforced) community rules and norms increased adherence to those rules and norms. There is, however, weak or mixed evidence about the effectiveness of a platform prompting (unenforced) norm when those norms are not set by a community; those “civility prompts” - as we term them - may even backfire.

In the Matias (2019) study, the fact that the increase in new users posting is larger than the increase in rule-abiding by new users may paradoxically create a higher overall number of non-rule-abiding posts (and therefore a higher workload for moderators).

It should also be noted that the norms discussed above are "prescriptive" or "injunctive"; that is, they refer to statements and beliefs about what people should do. They are not "descriptive" norms, which refer to what people actually do.