Atto reads the booking server's own clock — not your phone's — and then shows you the one thing every other timer hides: how accurate that reading actually was.
Download on the App StoreiPhone · iOS 17 or later · Free · Ad-supported · One-time purchase to remove ads
A "high accuracy" setting tells you nothing. Atto computes an error bar on every sync and puts it on screen, next to what produced it.
One response only narrows the offset to a second-wide window — but that window is a hard constraint, and probes at different phases of the server's second constrain different edges. Atto walks the phase in 137 ms steps, then predicts the tick and aims straight at it.
When a CDN answers for the origin, the timestamp inside froze when it was stored. Atto reads the Age and cache-status headers and drops those samples outright rather than averaging them in. Reading a stopped clock and calling it a sync is the worst mistake this app could make.
An oscillator off by a few parts per million turns a perfect sync into a soft one within the hour. Atto fits the slope between syncs by weighted least squares, extrapolates it to now, and tells you how many seconds a day your device loses.
A floating window sits on top of the queue. The Dynamic Island does not.
iOS draws the seconds itself, every frame. Atto hands it a target with the device clock's measured error already subtracted, so that native timer lands on the true server instant. Milliseconds the system cannot animate, so the app pushes them ten times a second in the final stretch — and hides them the rest of the time rather than showing a stale digit.
From your chosen lead the taps get firmer every second, then a hard burst at zero. The whole pattern goes to Core Haptics up front instead of being driven by a timer, so zero does not move even if the interface stutters.
Practice mode times the real gap between feeling the buzz and your tap registering, takes the median across attempts, and applies it as lead compensation. Your thumb, your latency, your number.
No app on iOS can suppress another app's notifications, and none can switch on Do Not Disturb. Atto says so plainly, then does the three things that work.
Atto exposes an “Arm countdown” action. Pair it with “Set Focus” in a time automation and the phone silences itself and arms the countdown without you touching anything.
With your permission Atto reads whether a Focus is active — one bit, nothing about which one — and warns you while the countdown is armed and nothing is holding notifications back.
The strongest option, and entirely yours to enable: Accessibility › Guided Access, then triple-click the side button on the booking page. Banners and calls are blocked outright and app switching is locked.
The usual approach in this category, and the choice Atto makes instead.
| Aspect | Usual approach | Atto |
|---|---|---|
| Accuracy | Low / medium / high, higher tiers gated | Always maximum, with the measured ±ms on screen |
| Method | Repeated sampling, averaged | Interval intersection, phase-aimed probes, SNTP cross-check |
| Cached responses | Used without distinction | Rejected via Age and cache-status headers |
| Device drift | “Please sync again” | Measured in ppm and extrapolated to the present |
| Display | Floating window, each size paywalled separately | Dynamic Island and Lock Screen — one rewarded ad per countdown, or a one-time purchase |
| Zero alert | A vibration on the second | Pre-scheduled Core Haptics ladder, no timer jitter |
| Lead compensation | A fixed recommended value per site | Your own reaction time, measured in practice mode |
| Price | Ads, plus tiers to remove them | Free. Accuracy and the countdown are never gated; no ad in the final 5 minutes. One purchase removes ads for good |
Bundled lists across four categories, with search, favourites and custom URLs. Both NTP and HTTP.
Ticketmaster, Ticketmaster UK, AXS, Live Nation, SeatGeek, StubHub, Eventim, Eventbrite, DICE, Resident Advisor, e+, Lawson Ticket, Ticket Pia, tixCraft, KKTIX, Interpark, Yes24, Melon Ticket, TicketLink, Weverse Shop
NIST (United States), NPL (United Kingdom), PTB (Germany), NICT (Japan), KRISS (Korea), plus Apple, Google Public NTP, Cloudflare Time and pool.ntp.org — over SNTP on port 123
Nike SNKRS, adidas, Supreme, END., StockX, GOAT, POP MART, UNIQLO, KREAM, Musinsa, SSG.COM, and university course registration servers. Anything missing goes in through the URL field.
One response constrains the offset to a window of width one second plus the round trip. That window is a hard constraint, and probes fired at different phases of the server's second constrain different edges of it. Atto sweeps the phase in 137 ms steps so fourteen probes land fourteen different phases, then — once the offset is close — predicts the exact instant the server's second will tick and aims a probe at that edge. Intersecting the results folds the error down to roughly the round-trip time.
The queue opens when that server thinks the moment has arrived. Measured in practice, site clocks often sit tens to hundreds of milliseconds ahead of or behind national standard time. Atto counts down against the site's clock and measures standard time alongside it, showing you the difference between the two.
No. A phone's oscillator is off by a few parts per million, so the offset walks as time passes. Atto fits the slope between syncs by weighted least squares, reports it in ppm, extrapolates it to the present moment, and re-syncs on its own every two minutes while armed.
Seconds are drawn by the system every frame, so they are always right; Atto hands the system a target with the device clock's measured error already removed, so its native timer lands on the true server instant. Milliseconds cannot be animated by the system, so the app pushes them, about ten times a second inside the final ten seconds. Outside that window they are hidden rather than shown stale.
No app on iOS can, and Atto will not pretend otherwise. It warns you when nothing is silencing the phone, and exposes an Arm countdown action to Shortcuts so a time automation can switch on Do Not Disturb and arm the countdown together. Guided Access, enabled by you in Accessibility settings, blocks interruptions outright.
No. It sends a single HEAD request to read the clock. It never asks for your account and takes no part in the purchase.