Block Lists

Last Edit: Oct 19 2020

A Block List is a list of words that you can use to moderate chat messages. Stream Chat comes with a built-in Block List called profanity_en_2020_v1 which contains over a thousand of the most common profane words.

You can manage your own block lists and use the APIs to block or flag messages from your users. To do this you need to configure your channel type(s) with these two configurations: blocklist and blocklist_behavior. The first one refers to the name of the block list and the second must be set as block or flag.

  • Applications can have up to 15 block lists

  • A Block List can contain up to 10,000 words, each word can be up to 40 characters

  • Text matching is done with case insensitive word match (no prefix, post-fix support)

  • Messages are split into words using white spaces and hyphens (cookie-monster matches both "cookie" and "monster")

So for instance, if you have a block list with the word "cream" these messages will be blocked or flagged:

  • She jabbed the spoon in the ice cream and sighed

  • Cream is the best

  • Cream!

and it will not affect any of these

  • Is creamcheese a word?

  • I did not enjoy watching Scream

The default block list contains material that many will find offensive.

Setup example

Block Lists can be managed using the APIs like any other Chat feature. Here is a simple example on how to create a Block List and use it for a channel type.

// add a new block list for this app
await client.createBlockList({
   name: 'no-cakes',
   words: ['fudge', 'cream', 'sugar'],

// use the block list for all channels of type messaging
await client.updateChannelType('messaging', {
	blocklist: 'no-cakes',
	blocklist_behavior: 'block',

List available block lists

All applications have the profanity_en_2020_v1 block list available. This endpoint returns all block lists available for this application.

await client.listBlockLists();

Describe a block list

await client.getBlockList('no-cakes');

Create new block list

const words = ['fudge', 'cream', 'sugar'];
await client.createBlockList({
	name: 'no-cakes',

Update a new block list

await client.updateBlockList('no-cakes', {
	words: ['fudge', 'cream', 'sugar', 'vanilla'],

Delete a block list

When a block list is deleted, it will be automatically removed from all channel types that were using it.

await client.deleteBlockList('no-cakes');