Reactions

Stream Chat supports message reactions such as likes, hearts, and custom reaction types. Users can react to messages, and reactions can include custom data and scores for cumulative reactions.

Sending a Reaction

Add a reaction to a message using the sendReaction method. Each user can have one reaction of each type per message.

// Add a reaction. Returns the reaction that was created.
const FReaction Reaction = Channel->SendReaction(Message, TEXT("love"));

// Add a reaction with a score, for cumulative reactions
Channel->SendReaction(Message, TEXT("clap"), 10);

// Replace all existing reactions from this user with the new one
Channel->SendReaction(Message, TEXT("love"), 1, true);

// Custom data on a reaction is not supported by the Unreal SDK. Let us know if you
// need it: https://github.com/GetStream/stream-chat-unreal/issues

Reaction Parameters

Name	Type	Description	Default	Optional
message_id	string	ID of the message to react to
type	string	Reaction type. Each user can have one reaction of each type per message.
score	integer	Score for cumulative reactions	1	✓
user_id	string	User ID (required for server-side calls)		✓
enforce_unique	boolean	If true, replaces all existing reactions from this user with the new one	false	✓
skip_push	boolean	If true, do not send a push notification	false	✓
emoji_code	string	Unicode emoji for push notification display		✓
custom data	object	Custom fields for the reaction		✓

Warning:

Custom data for reactions is limited to 1KB.

Removing a Reaction

Remove a reaction by specifying the message ID and reaction type.

// DeleteReaction takes the reaction itself rather than its type, so look up this
// user's reaction of that type on the message first.
const TOptional<FReaction> OwnReaction =
  Message.Reactions.GetOwnReaction(TEXT("love"), UUserManager::Get());
if (OwnReaction.IsSet())
{
  Channel->DeleteReaction(Message, OwnReaction.GetValue());
}

Field	Type	Description
reaction_counts	object	Count of reactions per type. Example: `{"love": 3, "fire": 2}`
reaction_scores	object	Sum of scores per type. Equals counts for standard reactions; differs for cumulative reactions.
reaction_groups	object	Detailed statistics per type including count, sum_scores, first_reaction_at, last_reaction_at
latest_reactions	array	The 10 most recent reactions with type, user_id, and created_at
own_reactions	array	The current user's reactions on this message

Use reaction_groups instead of reaction_counts for if you're building a custom implementation. The reaction_groups field provides additional metadata including timestamps and is the recommended approach.

To retrieve more than 10 reactions, use pagination.

Paginating Reactions

Retrieve reactions with pagination using limit and offset parameters.

Parameter	Maximum Value
limit	300
offset	1000

// Each message already carries a snapshot of its reactions, grouped by type.
for (const TPair<FName, FReactionGroup>& Group : Message.Reactions.GetReactionGroups())
{
  const FName Type = Group.Key;
  const int32 Count = Group.Value.Count;
  const int32 TotalScore = Group.Value.TotalScore;

  // The most recent reactions of this type that we hold locally. Note that Count may
  // exceed LatestReactions.Num(), which is what pagination below is for.
  for (const FReaction& Reaction : Group.Value.LatestReactions)
  {
    const FString ReactingUserId = Reaction.User->Id;
  }
}

// Did the current user react with this type?
const bool bLiked = Message.Reactions.GetOwnReaction(TEXT("love"), UUserManager::Get()).IsSet();

// Get the first 10 reactions from the API
Channel->GetReactions(
  Message,
  {10},    // FPaginationOptions: Limit, Offset
  [](const TArray<FReaction>& Reactions)
  {
    // Do something with Reactions
  });

// Get reactions 11-13
Channel->GetReactions(
  Message,
  {3, 10},
  [](const TArray<FReaction>& Reactions)
  {
    // Do something with Reactions
  });

Querying Reactions

Filter reactions by type or user on a specific message. This endpoint requires the user to have read permission on the channel when called client-side.

// Querying reactions with a filter is not yet available in the Unreal SDK.
// Please let us know if you'd like this feature implemented: https://github.com/GetStream/stream-chat-unreal/issues
// Use Channel->GetReactions to page through a message's reactions instead.

Cumulative Reactions

Cumulative reactions allow users to react multiple times to the same message, with the total score tracked. This is useful for features like Medium's "clap" functionality.

Set a score value when sending the reaction. The API returns:

sum_scores: Total score across all users
Individual user scores

// User claps 5 times
Channel->SendReaction(Message, TEXT("clap"), 5);

// Same user claps 20 more times (total becomes 25)
Channel->SendReaction(Message, TEXT("clap"), 25);