Signal flag Uniform

Red and white quarters.

Also known as: Uniform flag, Code flag Uniform

Sometimes confused with: U pennant

Maps & navigationSafety & hazardStandard profile

Meanings

The International Code of Signals flag for the letter Uniform, whose single-flag meaning is: You are running into danger.

Officially standardisedVerified fact
Flown alone, signals: You are running into danger.
Contexts: Public information, Navigation
Historically documentedVerified fact
Addressed entirely to the other vessel, and among the small number of Code signals a shore station will fly to a ship.
Contexts: Public information, Navigation

A rectangular flag quartered red and white, the red quarters diagonally opposite each other.

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

IMO Resolution A.1116(30), Escape route signs and equipment location markings
International Maritime Organization · retrieved 2026-08-22
The resolution text is not reproduced here and has NOT BEEN READ in full. Registered so records can state that a life-saving appliance marking is defined by the IMO rather than by convention, and which broad class it belongs to. See docs/paywalled-standards.md.
ITU Radio Regulations and the maritime signalling appendices
International Telecommunication Union · retrieved 2026-08-27
Cited for the identity of maritime and radio signalling conventions defined by the ITU. Not cited for national licensing arrangements.

Last reviewed 2026-08-27

Meanings

The International Code of Signals flag for the letter Uniform, whose single-flag meaning is: You are running into danger.

Officially standardisedVerified fact

Flown alone, signals: You are running into danger.

Historically documentedVerified fact

Addressed entirely to the other vessel, and among the small number of Code signals a shore station will fly to a ship.

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

Sources

IMO Resolution A.1116(30), Escape route signs and equipment location markings
International Maritime Organization · retrieved 2026-08-22
The resolution text is not reproduced here and has NOT BEEN READ in full. Registered so records can state that a life-saving appliance marking is defined by the IMO rather than by convention, and which broad class it belongs to. See docs/paywalled-standards.md.
ITU Radio Regulations and the maritime signalling appendices
International Telecommunication Union · retrieved 2026-08-27
Cited for the identity of maritime and radio signalling conventions defined by the ITU. Not cited for national licensing arrangements.

Last reviewed 2026-08-27