Time units (microseconds)

Every time field in cutcli is microseconds (μs) — captions, images, audios, keyframes, transitions, animations.

The conversion

1 second = 1,000,000 microseconds

Wanted duration	Write
0.1 s	100000
0.5 s	500000
1 s	1000000
3 s	3000000
10 s	10000000
1 min	60000000

Why microseconds

• Matches CapCut's internal storage format — no precision loss
• Keyframes / transitions / animations can be controlled to the microsecond
• Cross-platform safe, no float rounding

Reading start / end

timeline →
0           3,000,000           6,000,000        (microseconds)
[caption A  ][   caption B    ]
start=0    end=3M  start=3M    end=6M

start is when the segment begins on the overall timeline; end is when it ends. The duration is end - start.

Don't overlap inside a single track

Within one caption / video / audio track, neighboring segments must satisfy start ≥ previous end. Otherwise CapCut will render the timeline incorrectly.

Helpful shell snippets

Convert seconds to microseconds:

to_us() { echo $(( $1 * 1000000 )); }

START=$(to_us 0)        # 0
END=$(to_us 3)          # 3000000
echo "Caption from $START to $END"

Decimal seconds (e.g. "3.5 s"):

to_us_decimal() { python3 -c "print(int(float('$1') * 1000000))"; }
to_us_decimal 3.5    # 3500000

Common mistakes

Symptom	Likely cause
Caption flashes for one frame	You wrote ms: {"start":0,"end":3000} should be 3000000
Keyframe animation is way too fast	Same ms / μs confusion. Keyframe offset is also μs
Entrance animation longer than the segment	inAnimationDuration + outAnimationDuration must be ≤ end - start

More

• Coordinate system & positioning