# Duplicate Detection

Source: https://supernotify.rhizomatics.org.uk/latest/configuration/dupe_detection/

Three duplicate detection policies are available:

1. `dupe_policy_message_title_same_or_lower_priority`
   - Suppress messages with the same message and title that appear within the time to live period, unless the newer message has a higher priority.
   - This is the default, including if there is no `dupe_check` section configured
1. `dupe_policy_message_title_same`
   - Suppress messages with the same message and title that appear within the time to live period. Ignore priority.
1. `dupe_policy_none`
   - Don't suppress duplicate messages at all.

Messages and titles are stripped of digits and punctuation before being compared, so two messages with different counts, timestamps etc will be detected as duplicates.

## Configuration

The hashed message and title is cached, with a limit to both cache size and time the data is held. The `ttl` not only affects how much data is held in memory, it also controls after how long the same message can be repeated without being suppressed as a duplicate.

## Overriding

Set `force_resend: true` on the top level of the notification action data to override any dupe detection, just for that message.

## Internals

The cache is implemented using [cachetools TTLCache](https://cachetools.readthedocs.io/en/stable/#cachetools.TTLCache)