Indeterminate progress does not convey time remaining
Aliases: undetermined bar · sliding bar · unknown total
What it is
Indeterminate progress only asserts that work is still happening: a bar that travels back and forth, a ring that keeps spinning, with no “how much is left.” It cannot be read as a time estimate. When people take sliding speed to mean “almost done,” they are inventing a signal the system did not send. The legal meaning of indeterminate progress is one sentence: the system is alive and the total is unknown. Adding “about a minute left,” or slowing the animation in the second half, is stepping over the line to speak a remainder it does not have.
Why it happens
A time estimate needs a rate and a remainder. An indeterminate bar has no remainder, so rate has nothing to attach to. Animation rate is designed, unrelated to work rate, and is the cue most easily mistaken for work rate. Lacking a ratio, people use heuristics: fast motion means nearly finished, stillness means stuck. So the indeterminate bar, while avoiding a fake ratio, leaks fake time through motion. The decisions it can actually support are narrow: still worth waiting (it is moving), or dead (it has stopped). Whether to wait another thirty seconds, whether to cancel and change a parameter—those it cannot feed. Put an indeterminate bar on a wait that needs those decisions, and people are missing structure, not comfort.
Where it stops holding
Indeterminate does not mean it can never upgrade. Once a total becomes measurable mid-flight (a file list appears, a byte count arrives), switch to determinate; do not stay indeterminate because the start was. Looping motion often equals the spoken phrase “still loading” for assistive tech, equally silent on remainder; give a text status, and do not let sighted users receive a different time hint from the bar. Pairing an indeterminate bar with elapsed seconds is legitimate—that is time already spent, not remainder. If users extrapolate elapsed into remaining, that is their heuristic; if the interface then writes “estimated,” it has become fabrication.
Applying it
- Copy on an indeterminate bar names the work (connecting, building the report), not how long it will take.
- Do not hint remainder by slowing, speeding, or looking “almost full”; keep motion even, or clearly decoupled from data.
- The moment a total is known, switch to a determinate bar, and do not map the indeterminate animation’s position onto a percent.
- Verify by hiding the copy and asking how much is left. If anyone offers a number, the motion language is already leaking fake time.