A printing apparatus comprising: a printing fluid cartridge configured to be mounted to a cartridge mounting portion comprising an optical sensor (114, 116) and at least one contact, the printing fluid cartridge comprising: at least one electrical interface (75, 76, 77) configured to allow an electrical access to an integrated circuit provided to the printing fluid cartridge and configured to be electrically connected to the at least one contact; a light attenuating portion (33, 88, 89) configured to be inserted between a light emitter and a light receiver of the optical sensor and to be detected by the optical sensor, and an engagement portion configured to contact an engagement member of the cartridge mounting portion in an inserted state and to push the engagement member in an opposite direction of the insertion direction, wherein the printing fluid cartridge is configured to be inserted into the cartridge mounting portion in an insertion direction in an upright position, and the printing fluid cartridge in the upright position has a width in a width direction, a height in a height direction, and a depth in a depth direction, wherein the width direction, the height direction, and the depth direction are perpendicular to each other and the depth direction is parallel with the insertion direction, and the engagement portion comprises an engagement surface, which extends in the width direction and the height direction and/or faces in the opposite direction of the insertion direction, the printing fluid cartridge further comprising a pivot member having a front end portion being configured to be positioned in a first position such that the front end portion is positioned below an upper end of the engagement surface, wherein the printing apparatus further comprises: a cartridge mounting portion to which the printing fluid cartridge is configured to be mounted, the cartridge mounting portion comprising: at least one contact configured to be electrically connected to the at least one electrical interface (75, 76, 77); an optical sensor (114, 116) configured to detect the light attenuating portion (33, 88, 89), and an engagement member configured to retain the printing fluid cartridge in the mounted position. a printing fluid cartridge configured to be mounted to a cartridge mounting portion comprising an optical sensor (114, 116) and at least one contact, the printing fluid cartridge comprising: at least one electrical interface (75, 76, 77) configured to allow an electrical access to an integrated circuit provided to the printing fluid cartridge and configured to be electrically connected to the at least one contact; a light attenuating portion (33, 88, 89) configured to be inserted between a light emitter and a light receiver of the optical sensor and to be detected by the optical sensor, and at least one electrical interface (75, 76, 77) configured to allow an electrical access to an integrated circuit provided to the printing fluid cartridge and configured to be electrically connected to the at least one contact; a light attenuating portion (33, 88, 89) configured to be inserted between a light emitter and a light receiver of the optical sensor and to be detected by the optical sensor, and an engagement portion configured to contact an engagement member of the cartridge mounting portion in an inserted state and to push the engagement member in an opposite direction of the insertion direction, wherein the printing fluid cartridge is configured to be inserted into the cartridge mounting portion in an insertion direction in an upright position, and the printing fluid cartridge in the upright position has a width in a width direction, a height in a height direction, and a depth in a depth direction, wherein the width direction, the height direction, and the depth direction are perpendicular to each other and the depth direction is parallel with the insertion direction, and the engagement portion comprises an engagement surface, which extends in the width direction and the height direction and/or faces in the opposite direction of the insertion direction, the printing fluid cartridge further comprising a pivot member having a front end portion being configured to be positioned in a first position such that the front end portion is positioned below an upper end of the engagement surface, wherein the printing apparatus further comprises: a cartridge mounting portion to which the printing fluid cartridge is configured to be mounted, the cartridge mounting portion comprising: at least one contact configured to be electrically connected to the at least one electrical interface (75, 76, 77); an optical sensor (114, 116) configured to detect the light attenuating portion (33, 88, 89), and an engagement member configured to retain the printing fluid cartridge in the mounted position. a cartridge mounting portion to which the printing fluid cartridge is configured to be mounted, the cartridge mounting portion comprising: at least one contact configured to be electrically connected to the at least one electrical interface (75, 76, 77); an optical sensor (114, 116) configured to detect the light attenuating portion (33, 88, 89), and at least one contact configured to be electrically connected to the at least one electrical interface (75, 76, 77); an optical sensor (114, 116) configured to detect the light attenuating portion (33, 88, 89), and an engagement member configured to retain the printing fluid cartridge in the mounted position.