← Web Printing API

v147 · proposed IWA API · member reference

WebPrinter.fetchAttributes()

Fetches printer capabilities and state, then replaces the handle cache. It is the source of truth for matching a job request to printer-supported values.

Proposal and implementation differ from the old overviewChromeStatus currently records this API as Proposed, not shipped. This reference follows the current WICG IDL and Chromium source; test in the intended IWA configuration and feature-detect rather than relying on the v147 label.

Syntax

printer.fetchAttributes()
// Promise<WebPrinterAttributes>

Inputs

No parameters. It queries the selected printer; request no capability value until this has resolved.

Outputs

Resolves to refreshed WebPrinterAttributes, including capability/default fields and printer state when provided. Chromium retains the original name and ID when replacing its cache.

Errors

Normative: communication failure rejects NetworkError. Chromium rejects NotAllowedError for denied permission, throws InvalidStateError if another fetch on the same handle is in progress, and throws NotSupportedError after context shutdown.

Context and permission

The IDL requires a secure, isolated context. The specification also defines the web-printing Permissions Policy with default allowlist self; Chromium additionally checks an isolated context and cross-origin isolation before getPrinters(). The current proposal requires express, origin-specific consent triggered by enumeration. The exact chooser scope, persistence, and whether a later operation prompts again remain user-agent UX, not a settled web contract.

Lifecycle, cancellation, and cleanup

One fetch per WebPrinter may be outstanding in Chromium. Await it before another fetch. A success updates the cache atomically from the caller’s perspective; no rate limit is standardized, though the explainer asks implementers to consider one.

Examples

async function getCurrentAttributes(printer) {
  try {
    return await printer.fetchAttributes();
  } catch (error) {
    if (error.name === "NetworkError") return null;
    throw error;
  }
}

Browser compatibility

Current public compatibility evidence (checked 2026-07-26)
RuntimeStatusEvidence
Chrome (general)Proposed and not released. ChromeStatus lists I2S desktop target 147, which is not release proof. Do not infer general desktop Chrome support.ChromeStatus
Current Chromium serviceImplemented only when built with IS_CHROMEOS && USE_CUPS; otherwise getPrinters() has no service and throws SecurityError.Chromium manager implementation
Android / mobileChromeStatus Android is null; no public mobile release exists. The current ChromeOS+CUPS-only service path does not expose the service on Android.ChromeStatus; implementation guard
FirefoxNo signal; no BCD member record found.ChromeStatus position; BCD API data
SafariNo signal; no BCD member record found.ChromeStatus position; BCD API data
webstatus.devNo feature entry found for this query; this is not proof of absence from browsers.webstatus query

Security and privacy

Printer names, IDs, capabilities and state can fingerprint a device and reveal printing activity. A compromised IWA could create unwanted jobs or denial of service. Minimize enumeration and polling, do not expose attributes to untrusted content, validate documents before submitting, and offer an app-level confirmation/audit trail. The spec requires isolation and consent; it does not make printer information non-sensitive.

Canonical sources