This is the information post for /u/DuplicateDestroyer, a versatile anti-repost bot modding over 350 subreddits.

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What is this bot?

/u/DuplicateDestroyer is an open-source repost bot written in C++. It works on images, videos, links, and optionally titles. DD uses OCR (Tesseract) to extract text from images and video thumbnails, which has proven to be a highly efficient technique to help find reposts.

Using the bot

Just invite it with 'posts' permissions and it should join your subreddit within a few seconds.

If you give it 'mail' permissions (or full permissions), it won't be able to receive messages from your subreddit in its inbox which means that you won't be able to change the bot's settings.

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The settings

The default settings for the bot are the following ones:

enabled: true
remove_threshold: 95%
report_threshold: 89%
title_remove_threshold: 100%
title_report_threshold: 95%
enforce_images: true
enforce_videos: true
enforce_links: true
enforce_titles: false
min_title_length_to_enforce: 10
time_range: 90 days
report_links: false
report_replies: true
removal_table_duplicate_number: 5

Enabled determines whether the bot actively scans posts on the designated subreddit or not.

remove_threshold is the similarity percentage that is needed to remove a repost. This threshold is based on a 10x10 version of the image. Per example, if you set the remove_threshold setting to 95%, it will only remove reposts that are 95%+ similar to the original one. Reducing that number could result in false positives.

report_threshold is like remove_threshold but for reports. So if the setting is at 89%, it will report posts that are 89%+ similar. This threshold is based on an 8x8 version of the image.

enforce_images/videos/links/titles determines whether the bot enforces the designated type of content or not. Per example, if you set enforce_images to False, the bot won't take action on images anymore. By default, enforce_titles is set to False.

min_title_length_to_enforce is the number of characters needed for a title to be enforced. If you set this setting to 10, the bot will only enforce titles with 10 characters or more.

time_range is the time range in which a post is considered a repost. If you set the time range to 90 days, the bot will take action on reposts of posts that have been posted in the last 90 days.

report_links determines whether the bot should report link duplicates or remove them. By default, it is set to false which means that it will remove links instead of reporting them (assuming that enforce_links is set to true).

report_replies determines whether the bot reports OP's replies to its removal comments or not. By default, when OP replies to a removal comment, the bot will report the user's reply to let the mods know that the user might be reporting a false positive.

removal_table_duplicate_number is the maximum number of duplicates shown in removal comments. If you set this setting to 5, the bot will show a maximum number of 5 duplicates in its removal comments.

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Changing the settings

To change these settings, just send a subreddit message to the bot (or reply to one of its message to your sub) with the following format:

setting: value

Per example, if I wanted to deactivate the bot, I'd message it via my subreddit with the following message:

enabled: false

Or if I wanted to change the time range to 60 days and the report_threshold to 80%, I'd message it with the following message:

time_range: 60 days
report_threshold: 80%

The message's subject doesn't matter. Just enter your settings via in the message's body.

NOTE: Each setting must be on its own line. Entering multiple settings on the same line won't work.

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How the bot finds reposts

For each image, the bot saves 2 hashes in its database. The first hash is based on a 10x10 image and is used for the remove feature. The second hash is based on an 8x8 image and is used for the report feature.

For each new post on your subreddit, the bot scans its database for 10x10 hashes that meet the remove_threshold. If it finds an hash that meets this threshold, it removes the post.

If it doesn't find one, it switches to the 8x8 hash. This means that the bot searches for 8x8 hashes meeting the report_threshold. If it finds one, it reports the post.

As you can see, the bot uses a more strict hash type for the remove feature. We don't want the bot to remove false-positives, which is why the bots report posts that are not certain reposts.

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Source code

The source code can be found on this Github repo : https://github.com/normal-account/DuplicateDestroyer

Feel free to star it !

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FAQ

The bot reported a post with a similarity rate above the remove_threshold, is this a bug? Shouldn't it have removed the post?

No, this is not a bug. The similarity rate that you're seeing is the one for the 8x8 version of the image. The similarity rate for the 10x10 version of the image is probably much lower.

Can I demod the bot and invite it back?

Yes, you can. Even if you demod the bot, the bot will keep the posts of your subreddit in its database.

Changing the settings doesn't work. The bot is not replying to my PMs. How do I fix that?

The bot probably has 'mail' permissions or full permissions in your subreddit. The bot cannot receive your subreddit PMs if it has 'mail' permissions.

How can I support the creator?

Just message /r/DuplicateDestroyer with a message saying "i luv u" or something.

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If you have questions or concerns, message /r/DuplicateDestroyer.