From the tour of Chemistry.se:

All questions are tagged with their subject areas. Each can have up to 5 tags, since a question might be related to several subjects.

This post is a guide on grasping the basic use of the $\color{blue}{\text{tagging system}}$ on Chemistry Stack Exchange.

Contents (Answers):

Further reading:

  • $\begingroup$ This is supposed to be a FAQ question, please post your answers and share your tagging knowledge! $\endgroup$
    – M.A.R.
    Oct 8, 2015 at 23:58
  • 5
    $\begingroup$ This is an awesome effort! $\endgroup$
    – Ana
    Oct 9, 2015 at 19:11

4 Answers 4


How to find out if a tag is good to have/make

I present to you, the MAR Tag Test™ (abbreviated as MATT), a short test with three possible responses to each question, designed as a crude way of diagnosing the health of a (imaginary) tag.

Imagine X, a tag$\,\ldots$

MAR Tag Test

1: Ignore spam. Some people used to tag stuff as or to prevent their closure and downvotes. Also, you should to ask one of the veterans in chat whether if people (mostly new users) tag their question with that tag simply because they want to pass the "must-add-tag" filter and the tag is irrelevant to their question.
2: A tag should be a tag, not more, not less. At most, the tag should only be on $\frac{1}{10}$th of an SE site's questions.

Each $\rm \color{green}{Yes}$ is +2 points, $\rm \color{#999999}{Partially}$ is +1, and $\rm \color{red}{No}$ is -1. If the score for is$\,\ldots$

  • $>16$, then that's an exceptionally good tag.
  • $16>\rm score>12$, then that's a good tag to have.
  • $12>$, then that's not a good tag; make sure you ask on meta before creating it, or if it exists make a meta post to ask for possible burnination (i.e. tag removal).
  • 1
    $\begingroup$ Regarding note two, do you want organic-chemistry, homework and physical-chemistry to be removed? $\endgroup$
    – wythagoras
    Oct 9, 2015 at 18:00
  • $\begingroup$ @Wytha this guide is useful, but general. The community here has accepted the existence of 'homework' because$\,\ldots$ They just did! It's not a normal tag, (Actually, it's a meta tag) and it's only meant for differentiating HW and non-HW questions. Same goes for organochem and phys-chem, since those tags are rudimentary enough for a clueless asker to apply, and decent enough to remain. But organochem is never as good a tag as say, identification. $\endgroup$
    – M.A.R.
    Oct 9, 2015 at 18:06
  • 1
    $\begingroup$ I think there may be another criterion: is the tag one that can really only be applied once there are answers to its questions? $\endgroup$ Oct 10, 2015 at 17:41
  • $\begingroup$ Is the MAR Tag Test really trademarked? :P $\endgroup$ Aug 14, 2017 at 16:01
  • $\begingroup$ Which software did you use to make this image? looks very nice! @M.A.R.ಠ_ಠ $\endgroup$ Mar 19, 2018 at 5:01

Using favourite tags to find cool content faster and ignoring boring stuff

You might be interested in some very specific topic and you want to easily identify questions, that are categorised in this topic. I come with great news for you. You can have "Favorite Tags". Favourite tags you already have show up below the "Hot Meta Posts" box on the right side of the page. And it looks something like that:
You can easily change them when you click edit (or in your profile preferences).

Another way is to hover over a tag box on the main page. There will be a small pop up with the tag-wiki excerpt briefly explaining what that tag is for and a few statisticss. In the top left corner there is a star. It will be grey for any tag you do not give special treatment. For me, one of these tags is , as it is very broad:
OC = meh.

By clicking on this star, you can add it to you favourite tags (and it will appear in the box on the right side). One of my favourite tags is and you can see that the star is now yellow.
It also gets a fancy yellowish background, so that it sticks out of the list.

On the other hand there might be tags you don't want to be bothered with. You can simply ignore them. In your profile page you have the option to grey them out or to hide them completely. If you ignore a tag, the little star is changed into a red cross. I have chosen to demonstrate that.
reaction = bah.

  • $\begingroup$ In the settings, you can also check "Hide ignored tags" - so the tagged question will be completely hidden from the Questions page, not just greyed out. $\endgroup$ Mar 19, 2018 at 5:02

Using tags in searching

Tags can be a very strong tool for searching. The more healthy a site's tagging system is, the more effective tag searching will be. Currently, is the second most applied tag on meta, which means users and editors on Chemistry Stack Exchange do care about tags. Let's get down to business, shall we?

To search using the tag , you need to type the syntax [lolic-chemistry] in the search bar. The result of a search for the tag is the same as clicking on the tag link. The tag search is highly versatile:

See also


I haven't seen the tags here, but to post my question I need to add at least one tag. What should I do/know?

Your best bet is the tags page.

Most probably the tags you want on your question are in the first page. If you type a part of the tag's name, the UI will suggest the matching tags. For example, if you type "org" in the tags, the tags , and will appear as suggestions. Tags are in lowercase and are separated by dashes (-), not spaces.

Please choose tags wisely. If you do so, you're saving up editing time which could be used for answering your question. To do so, bear these in mind when you're tagging:

  • When you're tagging your question as X, you want "experts and enthusiasts on X" to find your question more easily. On bigger Stack Exchange sites, tags play the most important rule in finding an answer to your question.
  • If you have a problem you faced

    1. During self-study
    2. When you were writing your homework
    3. When you were preparing for an exam

    then you should show your effort to get a decent answer.

  • Tags are meant to put your question in well-defined categories. It's best to apply at least two tags to any question you have.

  • If you can't see any tags on the first page of the "Tags" page which could apply to your question, chances are it's off-topic on our site.

See also


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