line-charts

A 2026 bake-off of leading open-source line-charting libraries. Every library draws the same four datasets with the same palette, so what you are comparing is the library — its default quality, its API, how it handles real-world messiness — and not someone's styling effort. View the source of each chart inline.

A modern rebuild of datopian/line-charts (2016). Zero build step — plain HTML + ES modules. Read ANALYSIS.md for method and EVALUATION.md for the verdict.

The libraries

D3

Low-level toolkit. The quality ceiling — you build every pixel.

~90 KB · ISC/BSD

Observable Plot

Concise grammar of graphics from D3's author. Great defaults.

~65 KB · ISC

Vega-Lite

Charts as declarative JSON specs you can lint and diff.

~320 KB · BSD-3

Plotly.js

Batteries-included. Zoom, pan, export, log toggle — all free.

~1.1 MB · MIT

Chart.js

The popular default. Small, friendly, canvas, big plugin scene.

~70 KB · MIT

Apache ECharts

Production-hardened. Built-in dataZoom, SSR, huge-series modes.

~330 KB · Apache-2.0

µPlot

The performance option. ~18 KB, 100k+ points in milliseconds.

~18 KB · MIT

Scorecard

Subjective, 1–5, from building the four charts on this site. 5 = excellent, 1–2 = weak. Full reasoning in EVALUATION.md.

Library	Default look	API ergonomics	Custom ceiling	Interactivity (built-in)	Perf (4k pts)	Bundle	A11y / SSR	Docs / ecosystem
D3	5	2	5	2*	5	4	4	5
Observable Plot	5	5	3	3	4	4	3	3
Vega-Lite	4	5	4	3	4	2	3	4
Plotly.js	3	4	3	5	4	1	3	4
Chart.js	3	4	3	4	3	5	3	5
Apache ECharts	4	3	4	5	5	3	5	4
µPlot	3	3	2	4	5	5	2	3

* D3 interactivity is 2 out of the box because there is no box — the crosshair on the D3 page is ~25 lines of hand-written code. Its ceiling is 5.

The four test charts

CO₂ at Mauna Loa, monthly — one series with trend + seasonality, plus a deseasonalised overlay. ~800 points, non-zero y-axis. Real NOAA data.
Electricity generation by source — five series, crossing lines, five-colour categorical legend.
Life expectancy, five countries — deliberate missing years: does the line break or bridge? Wide value range, COVID dip.
BTC-USD daily — ~4,000 noisy points. Render speed, zoom/pan, optional log scale.

Considered, not included (yet)

Highcharts — excellent, but not free for commercial use (paid licence). Deliberately excluded; everything here is permissive OSS.
Recharts / visx / Nivo / VisX — React-only; this site is framework-free. Worth a separate React-flavoured page.
Vega (full) — the layer below Vega-Lite; more power, much more verbosity. Vega-Lite represents the family here.
ApexCharts, Chartist, Frappe Charts, billboard.js — reasonable, but don't beat the seven above on any axis we care about.
LightningChart JS, Plotly + WebGL, deck.gl — for >1M points / GPU territory. Out of scope for "line charts for data stories and dashboards".

Palette is the validated categorical reference palette (colour-blind-safe, light + dark). Add a library: copy demos/uplot.html + demos/uplot.js, swap the CDN and the four render functions, add a card here.