mozilla/pdf.js · error · FormatError

Unsupported predictor: ${predictor}

Error message

Unsupported predictor: ${predictor}

What it means

Error "Unsupported predictor: ${predictor}" thrown in mozilla/pdf.js.

Source

Thrown at src/core/predictor_stream.js:33

import { DecodeStream } from "./decode_stream.js";
import { Dict } from "./primitives.js";
import { FormatError } from "../shared/util.js";

class PredictorStream extends DecodeStream {
  constructor(str, maybeLength, params) {
    super(maybeLength);

    if (!(params instanceof Dict)) {
      return str; // no prediction
    }
    const predictor = (this.predictor = params.get("Predictor") || 1);

    if (predictor <= 1) {
      return str; // no prediction
    }
    if (predictor !== 2 && (predictor < 10 || predictor > 15)) {
      throw new FormatError(`Unsupported predictor: ${predictor}`);
    }

    this.readBlock = predictor === 2 ? this.readBlockTiff : this.readBlockPng;

    this.stream = str;
    this.dict = str.dict;

    const colors = (this.colors = params.get("Colors") || 1);
    const bits = (this.bits = params.get("BPC", "BitsPerComponent") || 8);
    const columns = (this.columns = params.get("Columns") || 1);

    this.pixBytes = (colors * bits + 7) >> 3;
    this.rowBytes = (columns * colors * bits + 7) >> 3;

    return this;
  }

  readBlockTiff() {

View on GitHub (pinned to 5903d58d58)

Solutions

1. Set the stream's /Predictor value to a supported predictor (1, 2, or 10-15); other predictor values are not supported.
2. If the predictor is valid but the PDF is non-conforming, regenerate the stream with a standard PNG/TIFF predictor value.

When it happens

Trigger: Thrown at src/core/predictor_stream.js:33 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/f51c94cf32d6b74d. Report an issue: GitHub.