read-only mode
Computing term for a mode where data can be read but not modified or written.
This file is opened in read-only mode.
読み取り専用 is the adjective form meaning 'read-only', while 読み取り専用モード specifically refers to the mode or state.
Compound of 読み取り (reading) + 専用 (exclusive use) + モード (mode), a direct translation of the English computing term 'read-only mode'.