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Updated July 2026 · real, multi-region App Store reviews
Head-to-head

Cardiio vs Instant Heart Rate

Cardiio 4.7★ · Free + IAP 60
Winner Instant Heart Rate
Instant Heart Rate 4.9★ · Free + IAP 75

Instant Heart Rate is generally preferred for its accuracy and ease of use, despite some recent issues with its free tier and subscription model, while Cardiio struggles with consistent readings and customer support.

Full reviews: Cardiio · Instant Heart Rate

Instant Heart Rate boasts a higher lifetime rating and more reviews, with users frequently praising its accuracy and simplicity, though recent updates and subscription practices have drawn criticism. Cardiio, while appreciated by some for its monitoring capabilities, is plagued by inconsistent readings, poor signal quality, and unresponsive customer support, making it a less reliable choice.

Head to head

Accuracy & Reliability edge: Instant Heart RateR1R4R7R18
Cardiio Cardiio users frequently report issues with 'poor signal quality' and difficulty getting consistent readings, especially on newer iPhone models R1R4R7R18. Some users find it inaccurate, with readings 'all over the place' .
Instant Heart Rate Instant Heart Rate is often praised for its accuracy, with users comparing it favorably to manual checks and other apps . However, some recent reviews indicate a decline in accuracy, with 'ridiculous numbers' or readings that are '20 points higher' than medical equipment . It also has issues with not reading low heart rates .
Ease of Use edge: Instant Heart RateR2R3R14R21
Cardiio Cardiio is described as 'simple' and 'easy' by some users R2R14. However, many users find it difficult to get a reading, requiring them to sit still without movement R3 or struggle with finger placement, especially on newer iPhones R21R36.
Instant Heart Rate Instant Heart Rate is generally considered 'simple, quick and easy' to use . However, some users report issues with the camera not turning on , difficulties with the sign-in process , or the measurement process being too fast or slow .
Features & Functionality edge: Instant Heart RateR5R9R11R16
Cardiio Cardiio helps users monitor heart rate, provides peace of mind, and can warn if heart rate gets too low or high R11. Some users were disappointed it didn't offer a waveform like an ECG or blood pressure monitoring R5R16. There are reports of the app crashing R9 and issues with the FAQ section linking to a gambling site R24.
Instant Heart Rate Instant Heart Rate offers heart rate monitoring, can detect palpitations and arrhythmias, and generates a plethysmogram . Users appreciate its ability to log past results . However, it does not provide blood pressure readings despite some advertising claims R94R97, and some users have lost readings after updates . There are also reports of inappropriate chat sites hijacking the app .
Price & Value tieR10R39R40R43
Cardiio Cardiio is advertised as free but often demands money after download R10. Users report being charged immediately after starting a 'free trial' or being billed without subscribing R40R43R55R58. Some users find the free version useful for approximate heart rate but don't see value in the pro version due to reliability issues R39.
Instant Heart Rate Instant Heart Rate is also advertised as free but many users report being charged immediately for subscriptions (around $60-70/year or $11/month) after starting a 'free trial,' or being unable to cancel . The free version has become very limited, with only 7 seconds of measurement, making it 'pretty useless' .
Customer Support & Privacy tieR6R12R24R43
Cardiio Cardiio users report a lack of developer response to concerns and help requests, making it 'virtually impossible' to get assistance R6R12R43. There are also reports of the app's FAQ section defaulting to a gambling site, raising security concerns R24.
Instant Heart Rate Instant Heart Rate receives strong criticism for 'horrible customer service,' with users finding it difficult to cancel subscriptions or get refunds . The app also requires a login/account creation, which some users view as a 'data risk' or 'pushy' .
Pick Cardiio if

You are looking for a basic heart rate monitor and are willing to tolerate inconsistent readings and potentially unresponsive customer support, especially if you have an older iPhone model where it might work better R18.

Pick Instant Heart Rate if

You prioritize accuracy and a generally easy-to-use interface for heart rate monitoring, and are prepared to navigate potential issues with subscription management and customer service .

Evidence note: Both apps have a significant number of negative reviews related to their 'free trial' and subscription models, indicating a common pain point for users across both platforms. Recent reviews for both apps show a decline in user satisfaction, particularly regarding accuracy and functionality on newer iPhone models.

Frequently asked

Do these apps provide blood pressure readings?
No, neither Cardiio nor Instant Heart Rate provide blood pressure readings directly from a finger R5R16R94R97. They primarily measure heart rate.
Are the 'free trials' truly free for these apps?
Many users report being charged immediately or within a day of starting a 'free trial' for both Cardiio and Instant Heart Rate, with charges ranging from around $11 to $70 for subscriptions, and difficulties in canceling to avoid these charges R10R40R55R58.
Do these apps work well on newer iPhone models?
Many users report that both Cardiio and Instant Heart Rate have issues with accuracy and getting readings on newer iPhone models, such as the iPhone 11, 12, 15, and 17 Pro Max, often attributing this to changes in camera and flash positioning R18R21R34R36.

What reviewers actually said

Built only from these 120 real reviews (foreign ones translated). Superscripts jump to the quote here. Apple has no per-review links, so [ref] opens that app's reviews on the App Store.

  1. [R1] Cardiio 1/5 · US Poor signal quality?: I will watch as the app measures my heart rate and stays in a very narrow range as I hold my finger over the camera for however long. It seems perfect, but then it just says “poor signal quality” with no other explanation. The signal quality was in fact not poor as I watched the data being collected and it seemed to be very consistent throughout the entire process. I need to
  2. [R4] Cardiio 1/5 · US Doesn’t work: Every time I used it, it measured the heart rate for quite a long time. Then, at the very end, it said “poor signal” and terminated. This is a terrible product. I deleted it, and I don’t miss it at all.
  3. [R7] Cardiio 1/5 · US Didn’t work: Every time I tried said poor signal and couldn’t do a reading no matter how I adjusted the light and camera. Other similar apps worked much better and actually worked. Disappointed.
  4. [R18] Cardiio 3/5 · US No longer accurate on iphone11: I loved this app to keep track of my irregular Heart rhythm when I had it in iphone8. It was very accurate. I upgraded to iphone11 and now it’s complete rubbish. It’s near impossible to get an accurate reading now. I guess it’s the light and camera lens positioning on the newer iPhone.
  5. [R2] Cardiio 5/5 · US Makes it simple!: I enjoy checking my bpm with this makes it so easy
  6. [R3] Cardiio 3/5 · US I like the app but I don’t like it: You literally got to sit still no movement period or it will not register. You guys need to fix that issue.
  7. [R14] Cardiio 5/5 · US Great App: Love how I can easily check my heart rate anywhere and anytime, especially if I’m not wearing my smartwatch.
  8. [R21] Cardiio 3/5 · US Pretty accurate: Difficulty placing finger in the correct position on iPhone 15
  9. [R5] Cardiio 5/5 · US No blood monitors: I’m enjoying the app but the only issue I have is that there is no blood monitor
  10. [R9] Cardiio 3/5 · US It will be best if the problems will be solved: It always crash when i go to insight tab or i save a heartbeat but its good to being free
  11. [R11] Cardiio 5/5 · US Great app: Woke up with racing heart, helped monitor the situation
  12. [R16] Cardiio 1/5 · US Buyer Beware: I thought by the “ heart rate checker and beat analyzer” description that this would actually give me a wave form like an ECG. All it does is give you the whip more like a pulse ox. I’m capable of counting my own pulse so this was a disappointment for me. I’m hoping to get a refund as it’s just been about an hour since I bought it and realized that it wasn’t what I thought it was.
  13. [R10] Cardiio 1/5 · US Scam: Claims it’s free, demands money for use after download.
  14. [R39] Cardiio 3/5 · US Useful enough...: The app is useful enough to get a roughly accurate pulse but so many things can go wrong with a reading (finger moving slightly, finger being cold, etc), I can’t see buying the pro version. The free version is great for approx heart rate.
  15. [R40] Cardiio 1/5 · US Cancelled before free trial expired: I did not subscribe to this thing. They are charging me for it.
  16. [R43] Cardiio 1/5 · US Tried to delete: This might be fantastic for those following it. I realized it wasn’t for me, so contacted them to stop billing & cancel my account. They won’t respond. So much for free trial! Zero impressed!
  17. [R6] Cardiio 3/5 · US Better Cardio Apps out there: I am having a problem with this app, and it is virtually impossible getting the developer to respond to my concerns.
  18. [R12] Cardiio 3/5 · US No response: Got the app It keeps waking me up with a reminder, wanted to stop it. Sent request for help same question four times So far no response
  19. [R24] Cardiio 3/5 · US FAQs??: What’s up with your FAQ section. It defaults to a gambling site in a foreign language. Has your app been hacked???
  20. [R94] Instant Heart Rate 2/5 · US Not at all what I thought: Mainly got this app for B/P. The app would only take my pulse
  21. [R97] Instant Heart Rate 1/5 · US Finger BP?: Several of this type of health app advertise having the ability to take BP directly from a finger. Blatant false advertising and they all need to take that down. If you want BP you will have to have a BP cuff.
  22. [R55] Cardiio 1/5 · US Beware: I signed up for a free trial and Apple billed me the very first day
  23. [R58] Cardiio 1/5 · US Terrible: Signed up for free trial and it did not work on my phone so I cancelled but they had in less than 24 hrs signed me up for the year. Does not work on my Apple 13 mini and my Apple Watch is much easier to use and very accurate. Worthless!
  24. [R34] Cardiio 1/5 · US Isn’t working properly: It was working excellent on iPhone 16 pro max but on iPhone 17 pro max 8 out of 10 times says poor signal!!!
  25. [R36] Cardiio 3/5 · US It won’t measure my heart rate now: I have had this app for awhile and it worked very well. Now it won’t measure without covering the flash, it didn’t do that before. I have 3 cameras and it worked fine before that.

Synthesized from 120 recent App Store reviews · updated July 2026 · View on the App Store