> ## Documentation Index > Fetch the complete documentation index at: https://www.cometchat.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Overview > Send, retrieve, and manage messages in one-on-one and group conversations. A **Message** is the core unit of communication in CometChat. Users can send text, media files, and custom data to other users or groups. Messages support threading, reactions, read receipts, and delivery tracking. ### Key behaviors * Maximum file upload size is **100 MB** per message (includes the file and the entire POST body). * The message JSON payload (including metadata) can be up to **65,536 characters (\~65 KB)**. * The `data` object within a message must not exceed **10 KB**. It accepts any JSON structure with UTF8mb4 encoding. * Messages can have up to **25 tags**, each up to 100 characters (UTF8mb4). * Soft-deleted messages remain in the database. Permanently deleted messages (via API) are removed entirely. * For groups with more than **300 members**, unread message counts and conversations are not updated. * Delivery and read receipts are sent for groups of up to **300 online users**. ### How messages connect to other resources * **Users** — Messages are sent by and delivered to [Users](/rest-api/users). The sender must be authenticated. * **Groups** — Messages can target a [Group](/rest-api/groups) by specifying the group's GUID as the receiver. * **Conversations** — Each message exchange creates or updates a [Conversation](/rest-api/conversations) that tracks the last message and unread count. * **Threads** — Any message can be a parent for a thread. Replies are managed via the [threaded messages](/rest-api/messages/list-threaded-messages) endpoints. * **Reactions** — Users can [add](/rest-api/messages/add-reaction) or [remove](/rest-api/messages/remove-reaction) emoji reactions on messages. ### Available operations | Operation | Method | Endpoint | Description | | ------------------------------------------------------------------------------------------ | -------- | ------------------------------------- | ------------------------------------------------ | | [Send Message](/rest-api/messages/send-message) | `POST` | `/messages` | Send a message to a user or group | | [List Messages](/rest-api/messages/list-messages) | `GET` | `/messages` | Retrieve all messages for the authenticated user | | [List User Messages](/rest-api/messages/list-user-messages) | `GET` | `/users/{uid}/messages` | Retrieve messages in a 1-on-1 conversation | | [List Group Messages](/rest-api/messages/list-group-messages) | `GET` | `/groups/{guid}/messages` | Retrieve messages in a group conversation | | [Get Message](/rest-api/messages/get-message) | `GET` | `/messages/{id}` | Retrieve a specific message by ID | | [Update Message](/rest-api/messages/update-message) | `PUT` | `/messages/{id}` | Edit a sent message | | [Delete Message](/rest-api/messages/delete-message) | `DELETE` | `/messages/{id}` | Soft-delete or permanently delete a message | | [Send Threaded Message](/rest-api/messages/send-threaded-message) | `POST` | `/messages/{id}/thread` | Reply to a message in a thread | | [List Threaded Messages](/rest-api/messages/list-threaded-messages) | `GET` | `/messages/{id}/thread` | Retrieve all replies in a thread | | [Send Bot Message](/rest-api/messages/send-bot-message) | `POST` | `/bots/{uid}/messages` | Send a message as a bot user | | [Add Reaction](/rest-api/messages/add-reaction) | `POST` | `/messages/{id}/reactions` | Add an emoji reaction to a message | | [Remove Reaction](/rest-api/messages/remove-reaction) | `DELETE` | `/messages/{id}/reactions/{reaction}` | Remove an emoji reaction from a message | | [List All Reactions](/rest-api/messages/list-all-reactions) | `GET` | `/messages/{id}/reactions` | List all reactions on a message | | [List Reactions by Emoji](/rest-api/messages/list-reactions-with-a-specific-emoji-unicode) | `GET` | `/messages/{id}/reactions/{reaction}` | List reactions filtered by a specific emoji | ### Message properties | Property | Type | Description | | ---------------- | ---------------- | ------------------------------------------------------------------------------------------------------------------------- | | **id** | integer | Unique message identifier. System-generated, read-only. | | **type** | string | Message type: `text`, `image`, `audio`, `video`, `file`, or a custom type. | | **category** | string | Message category: `message` or `custom`. | | **data** | object | Arbitrary JSON structure (max 10 KB). Recognized keys: `text`, `attachments`, `custom_data`, `metadata`. Accepts UTF8mb4. | | **tags** | array of strings | Tags for categorizing messages. Max 25 tags, 100 characters each (UTF8mb4). | | **sender** | string | UID of the user who sent the message. Read-only. | | **receiver** | string | UID (for user messages) or GUID (for group messages) of the recipient. | | **receiverType** | string | Receiver type: `user` or `group`. | | **sentAt** | integer | UNIX timestamp of when the message was sent. Read-only. | ### Error handling | Error Code | Description | | --------------------------- | ------------------------------------------- | | `AUTH_ERR_EMPTY_APIKEY` | API key is missing from the request headers | | `AUTH_ERR_APIKEY_NOT_FOUND` | The provided API key is invalid | | `ERR_MSG_NOT_FOUND` | The specified message does not exist | | `ERR_UID_NOT_FOUND` | The receiver UID does not exist | | `ERR_GUID_NOT_FOUND` | The receiver group GUID does not exist | For the complete list of error codes, see [Error Guide](/articles/error-guide). For all system limits (file upload size, message payload, tag counts, etc.), see [Properties and Constraints](/articles/properties-and-constraints).