Mastodon does not have a single global trending algorithm like traditional social platforms. Each instance maintains its own trending hashtags based on local activity. This means a hashtag popular on mastodon.social may not appear on your smaller instance. Finding trending hashtags across multiple instances requires using specific tools and features. This article covers the built-in instance trends, federated timeline observation, and external aggregators to discover what is popular across the fediverse.
Key Takeaways: How to Discover Trending Hashtags in Mastodon
- Explore > Trending hashtags: Shows the top hashtags on your own instance based on recent local and federated posts.
- Federated timeline: Browsing the federated feed reveals hashtags used by connected instances in real time.
- External tools like FediTrends: Aggregates trending hashtags from multiple Mastodon instances into a single searchable list.
How Mastodon Trending Works on Each Instance
Mastodon instances calculate trending hashtags independently. The server counts how many unique accounts used a hashtag within a recent time window, typically the last 24 to 48 hours. The algorithm applies a decay factor so older posts lose influence. Hashtags must be used by at least a few distinct accounts to appear in the trending list. This design prevents spam from a single account from dominating trends. Because each instance sees only its own local posts plus posts from federated instances it follows, trends vary widely. A hashtag trending on a large instance like mastodon.social will often appear on smaller instances that follow it. But a hashtag popular only within a niche instance may never reach others.
Prerequisites for Using Trending Features
You need a Mastodon account on any instance. The trending hashtag feature is available in the official Mastodon web interface and most third-party apps. There is no special permission required. If your instance administrator has disabled trending features, you will not see the trending section. In that case, use the federated timeline or external tools instead.
Finding Trending Hashtags Using the Explore Section
The Explore section is the most direct way to see trending hashtags on your instance. It is available in the left sidebar on the web interface and in the app drawer on mobile apps.
- Open the Explore page
On the web interface, click Explore in the left navigation menu. On the official Mastodon mobile app, tap the magnifying glass icon at the bottom of the screen. - Switch to the Trending hashtags tab
At the top of the Explore page, you see three tabs: Posts, Hashtags, and News. Click or tap Hashtags to view the trending hashtag list. - Review the list of hashtags
The page displays up to 10 trending hashtags. Each entry shows the hashtag name, the number of posts using it in the last 24 hours, and the number of unique accounts. Click any hashtag to see a timeline of posts that include it. - Refresh the list manually
Trending hashtags update every few minutes. To force a refresh, reload the Explore page. On the web interface, press Ctrl+R or F5. On mobile, pull down the screen to refresh.
Using the Federated Timeline to Spot Hashtags
The federated timeline shows public posts from all instances your server knows about. Watching this feed helps you spot hashtags that are gaining traction across many instances. This method works even if your instance does not show a trending section.
- Open the Federated timeline
On the web interface, click Federated in the left sidebar under the Live Feeds section. On mobile, tap the globe icon at the top of the timeline. - Scroll through posts and note repeated hashtags
Look for hashtags that appear in multiple posts from different accounts. Hashtags appear as clickable blue links. The more often a hashtag appears, the more likely it is trending. - Click a hashtag to see its dedicated timeline
Click any hashtag to open a timeline showing only posts that include it. This timeline spans all federated instances, not just your own. You can see how many posts were made recently. - Use the search bar to check a specific hashtag
Type the hashtag into the search bar at the top of the page. Mastodon shows a dropdown with matching hashtags. Select one to see its aggregated timeline. This confirms whether the hashtag is used across multiple instances.
Using External Tools to Aggregate Trends
Several third-party websites collect trending hashtags from many Mastodon instances and display them in one place. These tools give you a broader view than any single instance can provide.
FediTrends
FediTrends (fedtrends dot com) scrapes public trending data from over 100 Mastodon instances. It updates every hour. The site shows the top 20 hashtags globally, the top 20 per language, and a searchable archive. You can filter by language or instance size. This is the most comprehensive free tool available.
Mastodon Trending Hashtags Bot
Some instances run bots that post daily trending hashtag reports. Search for trending in your instance’s directory or on the Explore page. Follow a bot that posts trending hashtags from multiple instances. The bot typically includes the hashtag name, post count, and instance source.
Instance-specific Trend Pages
Large instances often expose their trending hashtags as a public JSON endpoint. For example, mastodon.social has /api/v1/trends/tags. You can access this URL directly in a browser. The JSON output lists each hashtag, its usage count, and the number of accounts. This method requires basic familiarity with raw JSON data but gives you unfiltered access.
Common Issues When Finding Trending Hashtags
Trending Section Not Visible in Your App
Some third-party Mastodon apps do not include the Explore or Trending section. Switch to the official Mastodon web interface or a full-featured app like Tusky for Android or Ivory for iOS. If the section is still missing, your instance administrator may have disabled trends. Use the federated timeline or FediTrends instead.
Hashtags Show Zero Posts or Are Outdated
Trending lists update only every few minutes. A hashtag may appear with zero posts if the cache has not refreshed. Reload the page after a minute. If the problem persists, the hashtag may have been removed by the instance moderator or the trending algorithm may have expired it.
Federated Timeline Shows Only Local Content
If your instance is small or has few connections to other instances, the federated timeline may show mostly local posts. This limits the variety of hashtags you see. Connect your instance to larger instances by following popular accounts on those instances. Alternatively, use FediTrends for a global view.
Mastodon Trending Hashtags: Instance Trends vs FediTrends
| Item | Instance Trends (Explore) | FediTrends (External Tool) |
|---|---|---|
| Data source | Single instance only | Aggregated from 100+ instances |
| Update frequency | Every few minutes | Every hour |
| Filter options | None | By language, instance size |
| Requires account | Yes | No |
| Best for | Real-time local trends | Cross-instance trend discovery |
Use instance trends when you want to see what is popular right now on your own server. Use FediTrends when you need a broader view of what is trending across the entire fediverse. Both methods complement each other.
You can now find trending hashtags on your own instance using the Explore section and on multiple instances using the federated timeline or FediTrends. Start by checking your instance trends daily to stay current with local topics. For global trends, add FediTrends to your bookmarks and review it weekly. To go further, learn how to follow hashtags as a column in your Mastodon client so you never miss a trending topic.