0.4.0 / 2026-07-10

PromLens is no longer maintained and has been archived. Much of its functionality has been merged into the Prometheus server's "Explain" tab, where it is kept up to date.

• [CHANGE] PromQL: The holt_winters function is now called double_exponential_smoothing, following its rename in Prometheus 3.0. #266
• [CHANGE] Logging: Switch from go-kit/log to Go's standard library log/slog. The log output format has changed. #149
• [CHANGE] Docker images are now also published to GHCR (ghcr.io/prometheus/promlens). #260
• [FEATURE] PromQL: Update the PromQL parser to Prometheus 3.13. This adds support for UTF-8 metric and label names and for all functions added since Prometheus 2.55, e.g. info(), sort_by_label(), mad_over_time(), and the native histogram functions (histogram_avg(), histogram_count(), histogram_sum(), and more). Experimental functions are always enabled in the parser; whether they can be evaluated is decided by the connected Prometheus server. #266
• [FEATURE] PromQL: Support the experimental extended range selectors (anchored and smoothed modifiers) and duration expressions (e.g. foo[5m * 2], step(), min_of()/max_of()) in the parser and tree view. Note that the expression editor does not recognize duration expressions and underlines them as errors; they still parse and execute correctly. #266
• [FEATURE] Autocomplete: Update codemirror-promql to 0.313.0, bringing expression editor support for the Prometheus 3.13 PromQL syntax. #266
• [FEATURE] Native histograms: Display native histogram results in the table view (count, sum, and bucket breakdown) and in the graph view (plotting the histogram sum). #266
• [FEATURE] PromQL: Support the limitk() and limit_ratio() aggregations and the experimental fill()/fill_left()/fill_right() binary operator modifiers in the parser, tree view, editors, and explain views. #266
• [FEATURE] Display warnings and infos returned by the Prometheus query API next to query results and tree nodes. #266
• [ENHANCEMENT] Mark experimental PromQL functions with an "experimental" badge in the function explain view, and add missing short descriptions for the trigonometric functions. #266
• [ENHANCEMENT] Update all Go dependencies to their latest versions and build with Go 1.26. #266
• [ENHANCEMENT] Set datasource ID from URL query parameters. #112
• [ENHANCEMENT] Completely revamp the vector-to-vector binary operation matching visualizer. #124
• [ENHANCEMENT] Add atan2 binary operator support. #117
• [BUGFIX] PromQL: Quote UTF-8 metric and label names when serializing queries (selectors, by/without, on/ignoring, group_left/group_right), and escape control and other non-printable characters in strings like Prometheus does. #266
• [BUGFIX] URL-encode metric and label names in Prometheus API requests, fixing metadata lookups for UTF-8 names. #266