Mobile App Stability
Outlook 2024

The New Normal for Stability Standards

Definition: The percentage of mobile app sessions that did not end with a fatal error.

Mobile apps maintained the relatively high stability rates recorded last year with only minor fluctuation across all percentiles. This year’s median crash-free session rate comes at 99.95%, confirming the high level of stability across all apps.

The top-performing mobile teams at the 75^th percentile maintained the near-flawless score of 99.99% crash-free sessions, solidifying ‘five 9s’ as a target for highly successful mobile apps. Finally, apps lagging behind at the 25th percentile showed a marginal improvement, scoring 99.77%.

Confirming past results, the data establishes a 99.95% crash-free session rate as the acceptable stability target to remain competitive on the app store, with anything lower inviting the displeasure of users.

iOS regains the lead

Android apps fail to maintain their leading position in stability, with this year seeing iOS score a median crash-free session rate of 99.91% versus Android’s 99.80%. This reversal is visible across the board with iOS scoring 99.98% versus Android’s 99.95% at the 75^th percentile and 99.66% versus 99.32% at the 25^th percentile.

Despite the change of fortunes, Android maintained a respectable level of app stability overall. Albeit a significant challenge, Android’s fragmentation is far from being an insurmountable obstacle to mobile app success, with near-flawless already proven to be achievable. Android teams must continue raising their stability targets and prioritize them to achieve good results.

Platform Breakdown

*Higher is better

A marked difference between industries

With a larger sample, this year’s report is able to include the breakdown of a wider range of industries with the addition of the Lifestyle/Sports, Social/Dating, Telecom, Travel/Airlines, and Staffing/Recruitment industries.

The Health/Fitness industry takes the lead in 2024 scoring a median of 99.98% crash-free sessions, followed closely by Social/Dating and Telecom at 99.97%. Trailing far behind the rest, Lifestyle/Sports scored a median crash-free rate of 99.67%, with the closest score for Media/Entertainment at 99.90%. This could be a reflection of the varied scenarios and environments these apps face due to the nature of their industry. The remaining industries registered a respectable median crash-free score between 99.92% and 99.96%.

The top-performing mobile teams across all industries outperformed last year’s results to set the pace, with only four industries scoring below an almost flawless 99.99% or above and only one scoring below 99.97% at the 75^th percentile.

Industry Breakdown

*Higher is better

Five-nines stability for five-star ratings 

As the primary standard against which mobile apps are judged by their users, app store ratings play a crucial in mobile success. Mobile teams that manage to achieve a high app store rating distinguish themselves from the competition, boosting their acquisition and retention rates and paving their way to success.

The data once again shows a clear correlation between crash-free rates and star rating, with apps under 3 stars scoring a significantly lower median of 99.82%, marginally lower than last year. At the 25th percentile, the lowest-performing apps make this correlation clearer, with apps rated between 3 and 4.5 stars scoring around 99.7% and ones above 4.5 stars scoring 99.84% at the 25th percentile.

This reinforces previous findings suggesting a ’critical stability threshold’ of around 99.7% crash-free sessions to reach a 3-star rating, and around 99.85% to exceed 4.5 stars.

App Rating Breakdown

*Higher is better

Application Not Responding errors (ANR)

Definition: Instances where an app is unresponsive to user input for more than five seconds, prompting the operating system to notify the app user.

Highly disruptive to the user experience, ANR errors are a severe stability issue for Android apps. Although showing a relatively marked increase over last year’s data, the incidence rate of ANR errors remains quite low at a median of 2.62 ANR errors per 10K sessions.

Surprisingly, the 0-3 stars bracket is the only bracket to show an improvement over last year with a median of 2.83 ANRs per 10K sessions, an improvement of around 36%. The remaining brackets registered medians between 2.02 and 2.92.

The increase in ANR incidence rate is also true for the low-performers at the 75^th percentile, with the 0-3 stars bracket the only one to show improvement over last year. This indicates that mobile app users have a higher tolerance than previously suggested, with the current data pointing to a significantly higher threshold of around 10 ANR errors per 10K sessions.

ANRs per 10K Sessions

*Lower is better

Out Of Memory errors (OOM)

Definition: App terminations by the operating system due to excessive memory usage.

Like ANR errors, OOM errors have a severe impact on the user experience. However, unlike ANRs, the median number of OOM errors across all apps registered a modest increase to 1.12 OOM errors for every 10K sessions, maintaining a very low incidence rate.

Contrary to last year’s data, breaking this down by app rating reveals a largely homogenous OOM incidence rate at medians between 0.94 and 1.34. This holds true across the 25^th and 75^th percentile showing no correlation between OOM scores and app store ratings.

Judging by the increased tolerance we observed for ANR errors, the critical threshold for OOM errors is similarly higher at around 10 OOM errors per 10K sessions above which app store ratings are impacted.

OOMs per 10K Sessions

*Lower is better

App hangs

Definition: Instances where an app is unresponsive to user input for more than two seconds, but less than five seconds.

Farther down the impact scale, app hangs are considerably frustrating for mobile users and frequently evolve into more severe stability issues.

This year’s data shows little change in the median number of app hangs per 10 thousand sessions, ranging from a low of 64 per 10K sessions for apps between 3-4 stars to 103 per 10K sessions for apps above 4.5+.

Although apps rated below three stars scored the highest incidence rate at 236 app hangs per 10K sessions at the 75^th percentile, they show a notable improvement of 30% over last year to approach the 200 threshold. The remaining app rating brackets did not register significant changes, staying around the 200 app hangs per 10K sessions to seemingly confirm the previously suggested threshold.

App Hangs per 10K Sessions

*Lower is better

Forced restarts

Definition: Instances where an app is manually forced to terminate, then restarted within 5 seconds.

Representing the ‘turn it off and on again’ reflex, forced restarts can be a useful indicator for frustrating user experiences.

The median number of forced restarts across all apps holds at 134 per 10K sessions, exactly the same as last year’s score. The breakdown by app store rating shows less variation between brackets than last year and does not reveal any clear trends or correlations. The same is true at the 75^th percentile, with all brackets hovering around the 250 forced restarts per 10K sessions mark.

Forced Restarts per 10K Sessions

*Lower is better