chartjs/Chart.js · error · Error

Unsupported decimation algorithm '${options.algorithm}'

Error message

Unsupported decimation algorithm '${options.algorithm}'

What it means

The decimation plugin's beforeElementsUpdate iterates datasets; for each that exceeds the threshold it switches on options.algorithm. Only 'lttb' and 'min-max' are implemented; any other value (including undefined when the user enables decimation with a non-default algorithm, or a typo) falls through to default and throws. The default dataset algorithm is 'min-max' (plugin defaults), so this fires only when the user explicitly sets an unsupported value.

Source

Thrown at src/plugins/plugin.decimation.js:277

            return this._decimated;
          },
          set: function(d) {
            this._data = d;
          }
        });
      }

      // Point the chart to the decimated data
      let decimated;
      switch (options.algorithm) {
      case 'lttb':
        decimated = lttbDecimation(data, start, count, availableWidth, options);
        break;
      case 'min-max':
        decimated = minMaxDecimation(data, start, count, availableWidth);
        break;
      default:
        throw new Error(`Unsupported decimation algorithm '${options.algorithm}'`);
      }

      dataset._decimated = decimated;
    });
  },

  destroy(chart) {
    cleanDecimatedData(chart);
  }
};

View on GitHub (pinned to cb02e1d207)

Solutions

1. Use one of the two supported algorithms: 'lttb' or 'min-max'.
2. If you need a different algorithm, disable the built-in plugin (plugins.decimation.enabled = false) and pre-decimate the data yourself before passing to Chart.js.
3. Double-check spelling and casing: 'min-max' (hyphenated), 'lttb' (lowercase).
4. Confirm the algorithm is set at the right scope (plugins.decimation.algorithm or dataset-level decimation.algorithm).

Example fix

// before
plugins: { decimation: { enabled: true, algorithm: 'minmax' } } // typo -> throws

// after
plugins: { decimation: { enabled: true, algorithm: 'min-max' } }

// Validate decimation config before passing it to Chart.js.
const SUPPORTED = new Set(['lttb', 'min-max']);
function validateDecimation(options) {
  const d = options?.plugins?.decimation;
  if (d?.enabled) {
    const algo = d.algorithm || 'min-max';
    if (!SUPPORTED.has(algo)) {
      throw new Error(`Unsupported decimation algorithm '${algo}'. Use 'lttb' or 'min-max'.`);
    }
    for (const ds of options.data?.datasets ?? []) {
      const a = ds.decimation?.algorithm;
      if (a && !SUPPORTED.has(a)) {
        throw new Error(`Dataset decimation algorithm '${a}' is unsupported.`);
      }
    }
  }
}
validateDecimation(config);

// Constrain algorithm strings at the type level.
type DecimationAlgo = 'lttb' | 'min-max';
function isDecimationAlgo(s) { return s === 'lttb' || s === 'min-max'; }

When it happens

Trigger: Setting plugins.decimation.enabled = true together with plugins.decimation.algorithm = 'average' (or any non-'lttb'/'min-max' string, or a typo like 'minmax'); enabling decimation on a dataset and overriding algorithm per-dataset to an unsupported value.

Common situations: Assuming a decimation algorithm exists that does not (e.g. 'average', 'sample', 'pttb'); copy-pasting config from a tutorial for a different library; misreading docs and writing 'minmax' instead of 'min-max'.

Related errors

• class does not have id: ${item}
• ${min} and ${max} are too far apart with stepSize of ${stepS
• This method is not implemented: Check that a complete date a
• Cannot determine type of '${id}' axis. Please provide 'axis'
• "${id}" is not a registered ${type}.

AI-assisted analysis of chartjs/Chart.js@cb02e1d207 (2026-08-12). Data as JSON: /api/errors/64bd2a7bc5243478. Report an issue: GitHub.