[Guide] How to filter unwanted content? Creating custom filters

CruFox
The 1% - Hit 1% of Uploads Milestone for a year
Even Worse Kobold -
Birthday Fur - Joined within the first year of the site operation and has had significant amount of activity as of June 1, 2021.
Tag Master - Exceptionally Good and Proficient Tagger
Derpy Fur - Prevented Furbooru's terrible fate in April of 2021.
Dedicated Lifter  - Uploaded over 5k art pieces
Seedling - Gave the site life with many uploads during its first months
Heavy Lifter -
Astra - Helped choose the name for our mascot - Astra.
Passing of the Eclipse - Joined within the first month of public opening and has had at least some activity as of August 3, 2020.

Moderator
I like tags
Filtering out unwanted content is an important feature of Furbooru, this post is intended to explain the most important aspects of it.
 
Site Rule #4 states that:  
• If you see images that contain themes you do not like (…) you should add the appropriate tags to your filter.
• Do not indiscriminately downvote images based on their tags and/or content. Instead, filter content you do not wish to see.
 
If you don’t like some type of content please use your filters to hide it instead of downvoting.
 
To be able to filter things you first need to create a custom filter. To do this go to https://furbooru.org/filters/new and fill appropriate fields. You can also edit any of the preexisting filters by clicking on “Copy and customize” when you go to Filters page.
 
You can either just spoiler images containing certain tags or hide them entirely. Spoilered images will display a placehold image instead of the actual image. The behavior of the placeholder image can be changed from the dropdown menu in the upper-right corner:
 
full  
For example if set on “hover” then placeholder image will disappear when mouse cursor is placed on top of it:
 
full
 
Besides spoilering/hiding only individual tags you can also create complex expressions. Those will filter out all results of queries that you add here:  
full
 
For example the line
cat, safe
will cause all images tagged cat that are safe to be hidden (so images tagged cat that are not rated safe but instead suggestive, questionable, explicit, grimdark etc. will stay, unless those tags are hidden on their own). The line
raccoon, -dog
will hide all images with raccoons except those where there are also dogs, and the line
werewolf, -explicit
will cause all images tagged werewolf that are NOT explicit to be hidden (so only images tagged werewolf that are also tagged explicit will remain).
 
By using complex filter you can even hide all or some images uploaded by individual users. To do that go to their profile and click on “Uploads”:  
full
 
The part that needs to be copied into complex filter can be then found in the search bar, in my case it is:
 
full
 
For example to hide all images uploaded by me that are tagged with “fox” you need to add this text to your complex filter:
uploader_id:93, fox
 
if you want to hide everything uploaded by me add:  
uploader_id:93
 
More comprehensive list of available options can be found in Search Syntax Help.
 
full  
You can hide images based on their score, fave count, file extension, size, creation date, source url and many more.
 
 
When you are done, save it and then on the next page select “Use this filter”:
 
full
 
Once a custom filter is created and in use you can then either spoiler or hide individual tags by just hoovering over tags under an image and selecting appropriate option from the dropdown menu, the tag will be then added to your current filter:  
full
 
Hope this helps!
Anonymous #7878
I feel like that was really needed to be posted, thank you!  
It’s such a shame to see normal posts get downvoted, especially when there’s not that many upvotes to begin in the early phase of the website. Have there been any serial offenders caught using downvotes as “I don’t like” button yet, if you don’t mind telling us?
CruFox
The 1% - Hit 1% of Uploads Milestone for a year
Even Worse Kobold -
Birthday Fur - Joined within the first year of the site operation and has had significant amount of activity as of June 1, 2021.
Tag Master - Exceptionally Good and Proficient Tagger
Derpy Fur - Prevented Furbooru's terrible fate in April of 2021.
Dedicated Lifter  - Uploaded over 5k art pieces
Seedling - Gave the site life with many uploads during its first months
Heavy Lifter -
Astra - Helped choose the name for our mascot - Astra.
Passing of the Eclipse - Joined within the first month of public opening and has had at least some activity as of August 3, 2020.

Moderator
I like tags
@Anonymous #7878  
Yes there were, I PMed a few users about using filters instead of downvoting. One of the reasons I created this thread was that in the future I can show it to people who engage in indiscriminate downvoting instead of explaining how to use filters every time via PMs.
Litrojia
The 1% - Hit 1% of Uploads Milestone for a year
Birthday Fur - Joined within the first year of the site operation and has had significant amount of activity as of June 1, 2021.
Derpy Fur - Prevented Furbooru's terrible fate in April of 2021.
Seedling - Gave the site life with many uploads during its first months
Heavy Lifter - Uploaded over 1k art pieces
Artist -

Dang, even after using Derpi filters thoroughly for years, I never knew that new lines in complex filters create new expressions. I’ve been formatting everything as (expression 1) OR (expression 2) OR (expression 3) until now.
LP2Lily
Artist -
Birthday Fur - Joined within the first year of the site operation and has had significant amount of activity as of June 1, 2021.

Lily Fathom
I am hoping I can do more to filter tags. I have to ask; “when it comes to the anonymous user uploads is it possible to filter out specific things for those?”
 
Side note  
Still learning this taging system. I am very aware that my lack of understanding of the system may seem aggrivating. Not entirly sure I am breaking a rule by learning. I have a feeling that some of my questions seem flamitory to some. I do apologise if that is the case. I make mistakes because I am human.
CruFox
The 1% - Hit 1% of Uploads Milestone for a year
Even Worse Kobold -
Birthday Fur - Joined within the first year of the site operation and has had significant amount of activity as of June 1, 2021.
Tag Master - Exceptionally Good and Proficient Tagger
Derpy Fur - Prevented Furbooru's terrible fate in April of 2021.
Dedicated Lifter  - Uploaded over 5k art pieces
Seedling - Gave the site life with many uploads during its first months
Heavy Lifter -
Astra - Helped choose the name for our mascot - Astra.
Passing of the Eclipse - Joined within the first month of public opening and has had at least some activity as of August 3, 2020.

Moderator
I like tags
I have to ask; “when it comes to the anonymous user uploads is it possible to filter out specific things for those?”
It is possible to hide all uploads done by anonymous users. Just add this line to your complex hide filter:  
-uploader:?*
 
Yuo can of course combine this with other tags to make more specific filter that would hide anon uploads only for specific themes.
Syntax quick reference: **bold** *italic* ||hide text|| `code` __underline__ ~~strike~~ ^sup^ %sub%

Detailed syntax guide