Chart image endpoint

Endpoint

GET https://tgmcharts.com/api/v1/charts/{symbol}/{metric} renders a 1600×900 PNG (image/png) of the metric's stored history in TGMCharts' own chart style: line charts for daily valuation and yield series, bars for annual, quarterly and TTM statement series. The TGMCharts wordmark and the data-as-of footer are part of the frame — they are the attribution required by the API terms and no parameter removes them.

<img src="https://tgmcharts.com/api/v1/charts/AAPL/revenue"
     width="800" height="450" alt="AAPL annual revenue — data by TGMCharts" />

![KO dividend yield, 20 years](https://tgmcharts.com/api/v1/charts/KO/dividend-yield?years=20)

https://tgmcharts.com/api/v1/charts/KO/revenue?compare=PEP

What is in the frame

• Line series are downsampled to at most 300 evenly spaced points; bar series show the most recent 22 periods of the window.
• The headline shows the latest value in the window; the subhead states the basis (daily series, sampled about monthly, by fiscal year, by fiscal quarter, rolling trailing-twelve-month) and the year span; the footer carries the data-as-of date.
• A metric that is not meaningful for the company type, or a symbol with no stored history for it, renders an explanation card at 200 — an <img> embed degrades into a readable reason, never blank space or an invented series.
• Renders read stored, precomputed data only; no request waits on a live market-data call.

Chart metrics

Generated from the registry the endpoint reads. ?compare= is accepted on bar charts only.

Caching

PNG responses carry Cache-Control: public, max-age=3600, s-maxage=21600, stale-while-revalidate=86400, so a URL that has been requested once is served from the edge; the render refreshes with the daily data update. Do not cache-bust the URL — the same URL is the point.

Render limit

Keyless callers may start up to 30 new (uncached) renders per minute per IP address; cached URLs are not counted. Past the limit the endpoint answers 429 with Retry-After: 60 and the body below. A keyed request is exempt from this limiter and metered at 5 units per render against the account's tier quota instead — see authentication and limits.

{
  "error": "Render rate limit reached — cached chart URLs are unlimited; new renders are capped per minute. API keys lift this to tier quotas: https://tgmcharts.com/developers/keys",
  "upgradeUrl": "https://tgmcharts.com/developers/keys",
  "docs": "https://tgmcharts.com/developers/docs/authentication-and-limits"
}

Errors

• 400 — unknown query key, out-of-range years, compare on a line metric, or compare equal to the primary symbol.
• 404 — symbol not covered (onboarding hint), or a slug outside the chart tier (the body lists every chartMetrics slug).
• Error bodies are JSON; only successful renders are image/png.