Are hashtags still relevant in 2025? What communicators need to know

From trending topics to niche networks, hashtags have shaped how scientific content is found and followed online. But in 2025, as algorithms dominate discovery, are hashtags still worth using? 

The humble hashtag, born from a simple suggestion by Chris Messina on Twitter in 2007, revolutionised how we categorise and discover digital content. But, as we navigate an increasingly algorithm-driven social media landscape in 2025, many content creators are questioning whether hashtags still serve a purpose. The answer, like most things in science, isn't black and white 

The hashtag’s original purpose  

Hashtags were originally designed to bring people together around topics, events or ideas. They helped users track breaking news, follow conference updates, or connect with specialist communities - whether #MarineScience, #ADHDAwareness or #ECRChat. For science communicators, they were a neat way to improve reach and target like-minded audiences. But platforms have changed, and so has hashtag relevance. 

Algorithms, user behaviour and hashtag relevance 

Today's social media platforms operate on sophisticated algorithmic systems that analyse user behaviour, engagement patterns, and content quality to determine what appears in feeds. These algorithms consider hundreds of factors beyond hashtags: viewing time, engagement rates, user relationships, and even the time spent reading captions.  

Platform by platform reality check 

LinkedIn  

Hashtags still hold strategic value, especially for niche or industry-specific topics. They help surface posts in searches and recommended content feeds. But overusing broad tags like #Science or #Research won’t draw attention to your posts - they’re too saturated. 

What works:  

• 2–5 highly relevant tags  

• Combining broad and specific (e.g. #ScienceCommunication + #HealthEconomics)  

• Checking what hashtags your audience follows  

Instagram  

Instagram’s algorithm in 2025 prioritises content format and engagement more than hashtags. While tagging still helps categorise content, it’s no longer the discovery engine it once was. 

Still helpful for:  

• Labelling campaigns (#PlasticFreeJuly)  

• Browsing visual trends  

• Maintaining consistency across a campaign  

X (formerly Twitter)  

Hashtags are still relevant here — especially for trending conversations, events, and live updates. Whether you’re at a symposium or responding to breaking news, they boost visibility and help content ride the trending wave. 

Use for:  

• Events (#ScienceWeek)  

• Commentary on live or fast-moving topics  

BlueSky  

BlueSky, the decentralised social platform gaining traction among researchers and journalists, has taken a different path. It supports hashtags as part of search functionality, but discovery is often driven more by feed algorithms and community-curated lists than by tags. 

Current reality:  

• Hashtags work — but aren’t central  

• Communities often connect via shared feeds or invite codes  

• Use relevant tags sparingly to support discoverability  

Threads/Mastodon  

These platforms rely more on content relationships and follows than hashtags. Threads introduced ‘tags’ (their version of hashtags) globally in December 2023, but they're limited to one per post. Mastodon, in contrast, uses hashtags as a primary discovery mechanism since it doesn't offer algorithm-based content discovery by default. Hashtags are widely used on Mastodon for search, filtering, and content organization across various communities.  

Tip:  

• Use plain-language keywords for Threads, keeping in mind you can only use one tag per post 

• On Mastodon, 2–3 descriptive hashtags are welcomed and essential for discoverability (e.g. #PostdocLife, #EnviroData)  

Facebook and TikTok  

• Facebook: Hashtags have negligible engagement value. They’re often ignored by users and deprioritised by the algorithm.  

• TikTok: Discovery is increasingly driven by captions and in-video text. Hashtags can still support trend participation, but don’t influence reach as heavily as before.  

Hashtag strategy for science communicators  

If you’re creating digital content for a research centre, institute or collaboration, hashtags should support - not define -your strategy.  

Our top tips:  

• Don’t rely on hashtags for reach: craft valuable, audience-specific content first  

• Use hashtags to join conversations, not to start them  

• Align with the language your audience uses: search your tags before posting  

• Monitor performance: do your posts with hashtags actually perform better?  

Hashtags and the digital communication toolkit  

Rather than viewing hashtags as a yes or no option, think of them as one tool in an increasingly sophisticated digital communication toolkit.  

The hashtag isn't dead—it's evolved. 

In an era of algorithm-driven discovery, the most powerful hashtag remains the one that genuinely connects your scientific content with an audience wanting to engage with it. 

Need help navigating today’s digital platforms?  

We help research organisations craft smart, content strategies that connect with the right audiences—on the right platforms.  

Get in touch to sharpen your digital communications and make every post count.