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The signed change in an app's average rating across rolling time windows — typically 7-day, 30-day, and 90-day deltas. A rating delta of +0.03 over 7 days means the average climbed from (e.g.) 4.62 → 4.65; a delta of -0.10 means it dropped.
Also known as: rating change, rating trend, rating drift
Small numbers carry large information because a marketplace listing with 500+ reviews moves slowly under random noise: a 0.05-point drop in 7 days usually represents 20-50 negative reviews landing in concentrated time, not statistical drift — a signal worth investigating BEFORE the headline rating crosses a visible threshold or the marketplace's algorithm reweights the listing. AppRanks shows the per-window delta alongside the absolute rating on every app page so a stable 4.6 with a -0.08 v7d gets flagged differently than a stable 4.6 with a +0.02 v7d. The delta column is also where most early-warning signals first surface — a soft launch failing to convert, a competitor pulling installs away, or a quality regression triggering negative feedback.
Rating deltas are the earliest visible trouble signal on an established listing. By the time the absolute rating crosses below 4.5 — a common review-quality threshold for marketplaces — the underlying delta has typically been negative for weeks. Watching the delta lets a developer respond inside the window where corrective action (responding to recent 1-star reviews, shipping a hotfix, updating the listing FAQ) can still move the trajectory back. For competitive intelligence, a competitor's rating-delta turning negative two cycles in a row is often the leading indicator of an install-velocity reversal.
AppRanks computes rating deltas by snapshotting the rolling-window average rating at every scrape and diffing across the requested window (7/30/90 days). We do not annualize partial windows for apps newer than the window length — instead the delta is computed against whatever portion of the window has data, and the partial-window flag is surfaced on the timeline. Deltas are sign-preserving and rounded to two decimals.