Best Free Apps and Sites for Tracking the ISS and Satellites
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Spotting the ISS or a Starlink train with your own eyes is easy once you know exactly when and where to look — and that timing is the one thing you can’t guess. A handful of free tools do the actual math for you, using your location and up-to-date orbital tracking to tell you the pass start time, the direction, and how bright it will get.
This guide covers the tools worth actually using, what each one is good for, and how to pick the right one for tonight.
If you’ve read our guide on how to see the ISS from your backyard or our piece on spotting satellites with the naked eye, you already know the short version: satellites and the space station are only visible for a few minutes around dawn or dusk, and only during specific passes. Below are the tools that tell you when those passes happen, ranked roughly by how most people will end up using them.
Heavens-Above: the deep, detailed option
Heavens-Above (heavens-above.com) has been a go-to reference in the amateur astronomy community for a long time, and it’s still one of the most detailed free pass-prediction tools available. Set your location once (it remembers it in a browser cookie or account), and it will generate a table of upcoming ISS passes, along with passes for other bright satellites, plus general astronomy information like visible planets and comets.
What makes it useful beyond the ISS is the depth: it lists magnitude (how bright the pass will be), start/max/end times and directions, and it covers other satellites people don’t always think to track. It works entirely in a browser, and you don’t need an account just to look up basic pass times for your location. The interface is dated compared to a modern app, but the data underneath it is solid, which is why it’s stayed a staple for so long. If you only bookmark one website from this list, this is a strong candidate.
Spot the Station: straight from NASA
NASA runs its own dedicated ISS tracker at spotthestation.nasa.gov, and it’s worth using specifically because it comes straight from the source. You put in your location and it shows upcoming visible passes for the space station only — it doesn’t try to cover every satellite in orbit, just the one most people are actually looking for.
The standout feature is the alert option: you can sign up to get an email or text message ahead of a good pass for your location, so you don’t have to remember to check back. For a lot of casual sky-watchers, that’s the entire appeal — set it up once, then get notified when it’s actually worth stepping outside. Since it’s the ISS’s own agency running the tool, it’s about as authoritative as pass predictions get.
A dedicated mobile app: ISS Detector and similar
If checking a website ahead of time isn’t realistic for you, a dedicated mobile app is the low-effort option. ISS Detector is a well-known example: it’s built specifically to push a notification to your phone a few minutes before a good ISS or satellite pass, so you find out in real time instead of having to plan ahead.
Apps like this are available for mobile devices and typically offer a free version alongside an optional paid tier with extra features — we won’t quote specific pricing here since app store pricing changes, but the free tier is generally enough to get pass alerts working. The tradeoff versus a website like Heavens-Above is that you get less depth and fewer options, but you also don’t have to remember to look anything up. For people who want to catch passes without turning it into a hobby of checking a website every evening, this is the practical middle ground.
Starlink-specific trackers: for a launch you just heard about
None of the tools above are built for tracking a specific Starlink “train” after a recent launch, which behaves differently from a normal satellite pass — it’s a string of satellites still flying close together, visible only for a limited window of days after launch. That’s the gap a site like FindStarlink.com fills: it’s built specifically to track individual recent Starlink launches and predict when a visible train will pass over a given location.
General-purpose trackers aren’t set up well for something this specific and time-limited, so if you’ve heard about a recent Starlink launch and want to know if it’ll be visible from where you live, a dedicated Starlink tracker is the right tool for the job rather than trying to force Heavens-Above or Spot the Station to answer that question. We go into the full picture — what a train actually is and how long the window lasts — in our Starlink train guide.
Which one should you actually use?
| You want to… | Use this |
|---|---|
| Just catch the ISS tonight, simplest option | Spot the Station or Heavens-Above |
| Track a wider range of satellites with more detail | Heavens-Above |
| Check a launch you just heard about | A Starlink-specific tracker (e.g. FindStarlink.com) |
| Not have to remember to check at all | A phone app with push notifications (e.g. ISS Detector) |
In practice, a lot of people end up using two of these together: an app for the “don’t make me think about it” notification, and Heavens-Above or Spot the Station when they want to plan a specific evening or double-check exact timing before heading outside.
Once you’ve got a pass time
These tools only get you the “when” — the “how” is still up to you. Once you have a confirmed pass time, a pair of 7×50 binoculars is a natural pairing if you want to pick out more detail on brighter passes than the naked eye alone gives you (see our 7×50 binoculars and our full binoculars for stargazing guide). And if you’re waiting outside for a pass and need to check your phone or notes without wrecking your night vision, a small red torch does the job better than your phone’s white screen (more on that in our red headlamp guide).
Common questions
Do I need to create an account to use any of these?
No. Heavens-Above and Spot the Station both let you look up pass times for a location without signing up for anything — an account only matters if you want Spot the Station’s email/text alerts or want Heavens-Above to remember your location between visits.
Why do different tools sometimes show slightly different pass times?
Orbital data gets updated periodically and each tool refreshes on its own schedule, so times can shift by a minute or two, especially for predictions more than a few days out. Check again closer to the actual evening if precision matters to you.
Can these tools track things other than the ISS?
Heavens-Above does, showing a range of other bright satellites in addition to the ISS. Spot the Station is ISS-only by design, and Starlink-specific trackers are built around a particular category of satellite train rather than one object.
What to read next
- How to See the International Space Station From Your Backyard — the full walkthrough for planning and watching an ISS pass.
- Can You See Satellites With the Naked Eye? A Beginner’s Guide — what’s realistic to spot without any equipment.
- What Is a Starlink Train? When and How to See One — why trains look different from a normal satellite pass.
- How to Watch a Rocket Launch in Person: What You Actually Need — for when you want to see the launch itself, not just the aftermath.
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