ChromeOS Compatible - Scanner Specification v1.0

Version: 1.0.1
Last Updated: 2024-02-02

Legend

Product Verb	Development Action
"MUST"	Mandatory product requirement
"SHOULD"	Optional recommendation
"MAY"	Nice to have

Overview

This specification document outlines the scope and specifications for multi-function printers with scanning functions and single-function scanner devices to be ChromeOS compatible. The term "scanner" in this document refers to either type of device.

Scanning

The device must be compliant with Mopria's eSCL specification and scanning must be enabled by default. In addition to the requirements from the eSCL specification, ChromeOS has some specific expectations that are detailed below.

Network

The scanner device must support the following network protocols:

• Discovery through mDNS and DNS-SD as described in section 3 of the Mopria eSCL specification.
• HTTPS
  • The device must advertise this by registering a _uscans name.
  • TLS 1.2 or 1.3 for HTTPS connections.

The device must also implement the following behaviors with regard to network connectivity:

• The device must not redirect clients back to HTTP when a request is made over HTTPS.
• If the device uses a self-signed certificate for TLS, it should maintain the same certificate until the certificate expires or the user replaces it.

USB

The scanner must implement the following protocols and behaviors when using a USB connection:

• The device must support IPP-over-USB.
• The device must respond to eSCL requests over the IPP-over-USB tunnel by default.
• The device must respond to eSCL requests rooted at /eSCL through the IPP-over-USB tunnel regardless of the value of its rs field published to DNS-SD.
• The device must accept localhost as a valid value for the Host field for requests coming through USB.

Document sources

The scanner must support at least one of the following document sources:

• Platen
• Auto Document Feeder (ADF) (one-sided or duplex)

Other input sources may not work on ChromeOS.

• If the scanner has a duplex ADF, it must return all pages with the correct orientation as specified in the Mopria eSCL specification section 8.1.3.2.

Resolutions

The scanner must support at least one resolution within the range of 75–600 dpi.

• Resolutions outside this range may be supported in future ChromeOS versions.

Color Modes

The scanner must support at least one of the following color modes:

• 1-bit black and white (B&W)
• 8-bit grayscale
• 24-bit RGB (8 bits per pixel)

ChromeOS currently does not support 16-bit grayscale, 36-bit color (12bpp) or 48-bit color (16bpp). Support may be added in future ChromeOS versions.

Stored Jobs

ChromeOS does not currently support stored jobs / PIN scanning. If the device advertises this feature, it should clearly indicate "unsupported on ChromeOS".

Authentication

ChromeOS does not currently support authentication for scanning. If the device advertises this feature, it should clearly indicate "unsupported on ChromeOS".

Device-initiated Scanning

Most MFP devices with scanner functionality can initiate or control scanning from the device front panel. These features largely cannot be directly supported by ChromeOS. Scanners that offer front-panel or device-configured scanning features should indicate that they are not usable on ChromeOS unless they can be used without software running on the host computer. Several specific examples follow.

Scan to Computer

A scan is started from the device front panel, and the results are delivered directly to a computer (sometimes after allowing configuration on the computer before scanning). This is currently not supported on ChromeOS at all. If the scan to computer feature is advertised on product packaging, it must clearly indicate "unsupported on ChromeOS".

Note: As of 2023, There is currently no standard for passing device-initiated scans to a computer. If such a standard is identified or developed in the future, a future revision of this document may require this feature to support said standard.

Scan to Email

A scan is started on the device and sent via email. This is acceptable as long as the device can send email itself. SMTP and account information can be entered at the time of the scan or pre-configured with one of the acceptable configuration methods described in MFP spec: Connection Types.

If the device requires software that is not available on ChromeOS running on the computer to send the email on its behalf, it should clearly indicate "unsupported on ChromeOS".

Scan to Network Share, Google Drive, iCloud, SharePoint, etc.

A scan is started on the device and the results are saved directly to a network service of some kind. This is acceptable as long as the device can connect to the relevant service and save files itself. Account credentials can be supplied at the time of the scan or pre-configured using one of the acceptable configuration methods described in MFP spec: Connection Types.

If the device requires software that is not available on ChromeOS running on the computer to save the file on its behalf, it should clearly indicate "unsupported on ChromeOS".

Scan to USB or memory card

A scan is started on the device and the results are saved directly to a connected memory card or USB drive. This is acceptable as long as no additional software is required to complete the scan.

If the device requires software that is not available on ChromeOS running on the computer to save the file on its behalf, it should clearly indicate "unsupported on ChromeOS".

Photocopy

Photocopying is typically done through the device front panel. As long as the device handles copies itself, the feature and particular capabilities provided will not prevent certification.

If the device requires software that is not available on ChromeOS running on the computer to perform copying on its behalf, it should clearly indicate "unsupported on ChromeOS".

Note: ChromeOS may simulate copying by allowing the user to send a scanned document directly back to the printer. This is separate from any copying capability built into the device.

Scan to other destinations

Other destinations not described above will be handled on a case-by-case basis, but the same principle broadly applies: If the device can complete the operation itself (possibly after initial configuration), then the features do not need to block certification. If the device requires additional software that is not available on ChromeOS to complete scans to a specific destination, it cannot be certified.

If the device requires software that is not available on ChromeOS running on the computer to support the destination on its behalf, it should clearly indicate "unsupported on ChromeOS".

Revision history

Date	Version	Notes
2024-02-02	1.0.1	Fix links to other specs
2024-02-01	1.0	Initial Partner Site Publication