Watermarks

An invisible watermark is a signal embedded in the pixels or samples of the published file. It is meant to survive edits that strip a C2PA manifest, such as re-encoding, so that verification can search your account’s watermark bindings for the original; see Lookup and recovery. A recovered match is reported as recovery, never as cryptographic validity: the signed manifest is what establishes validity.

Only the decoded media types take a watermark: the embedded lane’s images, audio and video. Structural and sidecar formats are signed without decoding and carry none; see Formats.

Choosing a watermark

A watermark runs only in a recipe that includes one: “Sign + watermark” (rcp_system_watermark_then_sign_unfingerprinted), “Sign + watermark + fingerprint” (rcp_system_watermark_then_sign) or rcp_system_watermark_only. See Recipes for choosing between them.

• Omit watermark_algorithm and the job uses the default for the asset’s media type.
• Name the recommended algorithm to opt in to the one that ranks best in our watermark benchmark. Where it is already the default, naming it runs the same algorithm as omitting the field.
• Any other value must be one listed for that media type in GET /v1/capabilities.
• A job keeps the algorithm it was admitted with. A later change of default never reaches it.

The request rules and error codes are in Sign.

Strength

watermark_strength narrows the qualified strength ladder of the algorithm the job runs:

• subtle embeds at the lowest qualified strength only, and fails rather than embedding more strongly if the watermark would not be detected there.
• balanced is the default: exactly what omitting the field does.
• robust allows the full qualified ladder.

No level uses a strength outside the algorithm’s qualified ladder. The exact strengths per level are in the table below. See Sign for the request rules.

Soft binding

Some algorithms are on the C2PA soft-binding algorithm list. When one of them is embedded, the manifest records the watermark as a soft binding, so a C2PA validator can use it to find the manifest again. The others are not written as a soft binding.

Catalog

The tables below are generated from the capability snapshot the API is built with. A deployment can enable fewer, so GET /v1/capabilities stays the authority at run time.

Defaults

Modality	Default (field omitted)	Recommended	Selectable
audio	audioseal-mm02-4	audioseal-mm02-4	audioseal, audioseal-mm02-4
image	pixelseal	pixelseal	pixelseal, trustmark-b, trustmark-c, trustmark-p, trustmark-q, videoseal-image
video	pixelseal-video	pixelseal-video	pixelseal-video, videoseal

Modality	Why the default is what it is
audio	benchmark recommendation
image	benchmark recommendation
video	benchmark recommendation

Media types that take a watermark

Media type	Modality	Default	Selectable
audio/mpeg	audio	audioseal-mm02-4	audioseal, audioseal-mm02-4
audio/wav	audio	audioseal-mm02-4	audioseal, audioseal-mm02-4
image/avif	image	pixelseal	pixelseal, trustmark-b, trustmark-c, trustmark-p, trustmark-q, videoseal-image
image/jpeg	image	pixelseal	pixelseal, trustmark-b, trustmark-c, trustmark-p, trustmark-q, videoseal-image
image/png	image	pixelseal	pixelseal, trustmark-b, trustmark-c, trustmark-p, trustmark-q, videoseal-image
image/tiff	image	pixelseal	pixelseal, trustmark-b, trustmark-c, trustmark-p, trustmark-q, videoseal-image
image/webp	image	pixelseal	pixelseal, trustmark-b, trustmark-c, trustmark-p, trustmark-q, videoseal-image
video/mp4	video	pixelseal-video	pixelseal-video, videoseal

Algorithms

Algorithm	Name	Modality	C2PA soft-binding list
audioseal	Meta AudioSeal (streaming)	audio	Not registered
audioseal-mm02-4	Meta AudioSeal (streaming, quality-first)	audio	Not registered
pixelseal	Meta PixelSeal	image	Not registered
pixelseal-video	Meta PixelSeal (video)	video	Not registered
trustmark-b	Adobe TrustMark B	image	Not registered
trustmark-c	Adobe TrustMark C	image	Registered
trustmark-p	Adobe TrustMark P	image	Registered
trustmark-q	Adobe TrustMark Q	image	Registered
videoseal	Meta VideoSeal 1.0	video	Not registered
videoseal-image	Meta VideoSeal 1.0 (image mode)	image	Not registered

Strength levels

The qualified strengths each watermark_strength level allows, per algorithm:

Algorithm	subtle	balanced	robust
audioseal	0.5	0.5, 1.0, 1.1	0.5, 1.0, 1.1
audioseal-mm02-4	0.5	0.5, 1.0	0.5, 1.0
pixelseal	0.15	0.15, 0.2, 0.25	0.15, 0.2, 0.25
pixelseal-video	0.2	0.2, 0.4, 0.6	0.2, 0.4, 0.6
trustmark-b	1.0	1.0	1.0
trustmark-c	1.0	1.0	1.0
trustmark-p	0.8	0.8	0.8
trustmark-q	1.2	1.2, 1.3, 1.4, 1.5	1.2, 1.3, 1.4, 1.5
videoseal	0.4	0.4, 0.7, 1.1	0.4, 0.7, 1.1
videoseal-image	0.2	0.2	0.2