Threads topic tags let you attach one topic to a post, so people interested in that subject can find it. Each post gets a single topic tag, not a list of hashtags. If you include several #tags in the text, Threads uses the first valid one as the topic. The post itself can be up to 500 characters.
Key takeaways
- Threads topic tags are limited to one per post, and when a post contains several, the first valid tag is the one used.
- A topic tag is a way to place a post in a subject area, which is a different job from the hashtags used on Instagram.
- A Threads post can be up to 500 characters, and a post can include up to 5 unique links through the API.
- Choose a topic tag that names the subject of the post in words your audience would use, because a vague tag helps nobody find it.
- If you copy an Instagram caption to Threads, remove the hashtag block, since only one tag is used.
What are Threads topic tags?
A Threads topic tag is a single label you attach to a post to say what it is about. You add it by typing a # followed by the topic, similar to a hashtag. The difference is in how the platform uses it: Threads treats the tag as a topic for the whole post, and allows one per post.
Threads documents this in its API: a post carries one topic tag, and when text contains more than one #tag, the first valid one is the topic. That detail has a practical consequence. The order of your tags matters, and tags beyond the first do not behave as extra topics.
You are choosing one subject for the post, not stacking up as many search terms as the caption allows. If you are used to adding a dozen tags on another platform, Threads asks for a different habit.
How are topic tags different from hashtags?
Topic tags and hashtags share the # symbol, but they differ in how many you can use and what they are for. On Instagram, the Help Center states up to 5 hashtags per post. On Threads, the topic tag limit is 1. On LinkedIn there is no official limit. The table shows the contrast as of 2026.
| Platform | Hashtag or tag limit | Notes | |---|---|---| | Threads | 1 topic tag per post | The first valid #tag is used | | Instagram | Up to 5 hashtags per post | Help Center rule | | LinkedIn | No official limit | 3 to 5 is common advice | | YouTube | Hashtags ignored above 60 | All hashtags ignored if exceeded |
The takeaway is that the same caption can need a different tag setup on each platform. A hashtag list built for one will not translate to the next without editing.
Do other hashtags still work in Threads text?
You can type additional #words in a Threads post, but only the first valid tag counts as the post's topic. If you want a second subject to be visible, say it in words in the post. Further tags do not act as extra topics, so it is usually cleaner to leave them out.
How do you choose among Threads topic tags?
The best topic tag names the subject of the post as a reader would think of it. A few steps help you choose:
- Write the post first. Decide what the post is really about in one phrase.
- Turn that phrase into a tag. For a post about repairing a bike chain, the topic might be #BikeRepair, not #Tuesday or #Tips.
- Check it is a real topic. Type the tag in Threads and see what posts appear under it. If they look like yours, the tag fits.
- Choose between broad and narrow. A broad tag like #Cycling puts you among many posts. A narrow tag like #BikeRepair puts you among fewer but more relevant ones. Neither is wrong, and your goal decides.
- Keep a short list. Reusing a handful of topics builds a clear identity for your account over time.
Avoid tags that are just a joke or a feeling. They may be fun, but they do not place the post anywhere useful.
Where should the tag sit in the post?
The tag can sit anywhere in the text. Many people put it at the end so the opening reads naturally. If you place it in a sentence, make sure it is the first #tag in the post, since the first valid one is the topic. Check the order again if you edit the text, because moving a different tag to the front changes the topic.
What is the Threads post limit, and how do tags use it?
A Threads post can be up to 500 characters, according to the Threads API documentation. The topic tag is part of the text, so it uses some of those characters. A short tag costs little, but a long one in a short post is noticeable.
Emoji need attention. In the API, emoji count as their UTF-8 byte length, which means a single emoji typically uses 4 or more characters of the allowance. A post with a handful of emoji may therefore reach 500 sooner than you expect. As an illustration, ten emoji at 4 each use 40 of your 500.
A few other numbers from the same documentation:
- Links: up to 5 unique links per post through the API.
- Carousels: 2 to 20 items.
Because Threads is conversational, short posts often read best. The 500 limit is room to explain a point, not a target to fill. If your idea needs more, use a reply to continue the thought.
How do you adapt a post from another platform to Threads?
Adapting is mostly cutting and re-tagging. If you start from an Instagram caption, work through these steps:
- Trim the length. An Instagram caption can run to 2,200 characters, so it will often need cutting to fit 500.
- Remove the hashtag block. Keep one tag at most.
- Rewrite the opening. Threads reads like a conversation, so begin with the point or a question.
- Count again. Recount with the emoji rule in mind.
- Preview before you publish. Look at the final text as it will appear.
If you schedule posts, an automatic first comment, which is available on Threads in some publishing tools, can hold extra detail so the main post stays short. Make sure the main post still makes sense without it.
Frequently asked questions
How many topic tags can a Threads post have?
A Threads post has one topic tag. If you type several #tags, Threads uses the first valid one as the post's topic.
Are Threads topic tags the same as hashtags?
They look alike, since both use #, but they work differently. A topic tag assigns one subject to a post, while hashtags on Instagram can number up to 5 and act as separate labels.
What is the character limit for a Threads post?
A Threads post can be up to 500 characters. In the API, emoji count as their UTF-8 byte length, so they can use more than one character each.
How many links can a Threads post include?
Through the API, a Threads post can include up to 5 unique links. Carousels can have 2 to 20 items.
How MultiPost Studio helps
MultiPost Studio checks Threads posts against the 500-character limit, counts emoji the way the Threads API does, and flags posts that carry more than one topic tag. You can write a separate Threads version of a caption and preview it before it publishes. See what the composer checks for each platform.