Webhooks

Send a payload of merge variables to create a custom screen.

Before you begin

Learn how to build Private Plugins here. The guide below only explains how to use the "Webhook" data retrieval strategy.

Rate Limits

Request volume

You may send data to TRMNL's server up to 12x per hour. TRMNL+ subscribers may send up to 30x payloads per hour. Webhooks sent at a faster pace will receive a 429 rate limit response.

Request size

You may send up to 2kb of data. TRMNL+ subscribers may send up to 5kb of data. To stay within these boundaries while also creating a data rich experience, consider using the deep_merge and stream strategies documented below.

Authorization

TRMNL has Device API Keys, User API Keys, and Plugin Setting UUIDs. For private plugin screen generation, we'll use your Plugin Settings UUID.

This is accessible from your plugin instance's configuration form > Webhook URL field.

Private Plugin Webhook URL w/ UUID

Note: you must "save" (create) a private plugin instance to generate a UUID and Webhook URL.

Set new content

Send a POST request to your Webhook URL. Put data inside a merge_variables node like so:

curl "https://usetrmnl.com/api/custom_plugins/asdfqwerty1234" \
  -H "Content-Type: application/json" \
  -d '{"merge_variables": {"text":"You can do it!", "author": "Rob Schneider"}}' \
  -X POST

You will see this payload inside the Your Variables dropdown of the Markup Editor.

Your variables - available inside the Markup Editor

Get merge variable content

To fetch existing merge_variables from a private plugin, GET from the same endpoint:

curl "https://usetrmnl.com/api/custom_plugins/asdfqwerty1234"

Update existing content

If your private plugin needs to maintain state over time, for example an ever-growing todo list or a data visualization, you may prefer to send only "new" data points to your TRMNL plugin.

There are two strategies to accomplish this: deep_merge, and stream.

Deep merge strategy

The deep_merge strategy combines existing key/value pairs with the new values incoming on the webhook. It's a good way to update nested data with only a few values here and there.

curl "https://usetrmnl.com/api/custom_plugins/asdfqwerty1234" \
  -H "Content-Type: application/json" \
  -d '{"merge_variables": {"sensor": {"temperature": 42}}, "merge_strategy": "deep_merge"}' \
  -X POST

Stream strategy

The stream strategy is useful for accumulating values in arrays. Any top-level arrays are appended with the incoming values, and the stream_limit parameter ensures that old values drop off the arrays so they don't grow forever.

curl "https://usetrmnl.com/api/custom_plugins/asdfqwerty1234" \
  -H "Content-Type: application/json" \
  -d '{"merge_variables": {"temperatures": [40, 42]}, "merge_strategy": "stream", "stream_limit": 10}' \
  -X POST

Now you may iterate through the combined data inside your markup, for example:

Accessing streamed webhook data

Troubleshooting

For more help, see our Private Plugin guide or join the developer Discord from your account tab.