Samsung
Turn Auto Capitalize On or Off auf Samsung
The Samsung keyboard capitalizes the first letter of a new sentence by default. This behavior is controlled by the Auto capitalize option inside the Samsung Keyboard settings, part of the general typing behavior on One UI devices.
The keyboard detects sentence boundaries such as periods, line breaks, or newly opened text fields, then forces the next character to uppercase. This can clash with usernames, email addresses, code, or languages that do not follow the same capitalization rules as English.
Where to find the setting
Open Settings ➔ General management ➔ Samsung Keyboard settings ➔ More typing options and toggle Auto capitalize on or off.
Turning the option off stops the keyboard from changing letter case on its own; you then capitalize manually whenever needed. If autocorrect itself causes more trouble than capitalization does, check the separate Predictive text and Auto replace options instead - disabling auto capitalize alone will not calm down aggressive word suggestions.
The setting applies system-wide wherever the Samsung keyboard is active, including third-party apps, so the change carries over between messaging, browsers, and notes.