15 Second Timer — Free Countdown
Free online countdown — fullscreen, alarm, no signup
How to Use This 15 Second Timer
Set Duration
The timer is preset to 15 seconds. Click Set to confirm.
Initialize
Review the countdown display and enter fullscreen if needed.
Start
Hit Start to begin. The alarm sounds when time reaches zero.
Cast This Timer to a Bigger Screen
Mirror this countdown to any TV, projector, or display via Chromecast, AirPlay, or HDMI. Perfect for gyms, classrooms, sports facilities, or game events where everyone needs to see the same countdown.
Full casting guideCommon Uses for a 15 Second Timer
Tabata rest interval timing
The standard rest period in Tabata training. Pair it with 45-second work intervals to build a 1-minute circuit. Display it on the gym monitor so athletes know exactly when to start their next set.
Social media short video timing
The length of a social media story or short-form video. Use the countdown to practice delivering your message within the 15-second window.
Student quiz response window
A classroom response window long enough to think but short enough to keep energy high. Project the countdown so every student sees the same time pressure.
Warm-up drill intervals
Perfect for warm-up drill intervals in sports training. Cast it to the field or court display so coaches and athletes stay synchronized.
Fifteen seconds is a surprisingly useful interval — it's the standard rest period in Tabata training, the length of a social media story, and a classroom response window long enough to think but short enough to keep energy high. A 15 second online timer starts immediately with no configuration: large digits, automatic alarm, fullscreen display. For fitness use, it pairs perfectly with 45-second work intervals to build a 1-minute circuit. For classroom use, it gives students just enough pressure to focus without causing anxiety. Cast it to your gym TV or classroom projector so the whole room is working from the same countdown, without anyone needing to watch a phone.
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Fun Fact
Social media videos under 15 seconds consistently achieve the highest engagement rates across platforms. This insight drove TikTok's original format decision when it launched — videos were limited to exactly 15 seconds to maximize viewer retention and completion rates. Instagram Reels and YouTube Shorts later adopted similar short-form formats. Marketing research shows that shorter videos tend to be watched completely more often, which signals to algorithms that the content is engaging, resulting in broader distribution and reach.