Steam Mobile Authenticator
Steam Mobile Authenticator (also called Steam Guard Mobile Authenticator) is Valve’s two-factor app for login and trade confirmations. If the account sending items has been protected by it for fewer than 7 days, Steam may hold outgoing items for up to 15 days. Passing 7 days does not override other account or item restrictions.
Why activation date matters
Steam says outgoing items may be held for up to 15 days if the sending account has not been protected by Steam Guard Mobile Authenticator for at least 7 days. Adding the authenticator does not clear existing restrictions right away: Steam states that trades created within the first 7 days of adding it still carry a hold of up to 15 days. Trades created after that 7-day protection period are not subject to this specific authenticator hold, but other account restrictions and item-level locks may still apply.
How to enable it
1. Install the official Steam Mobile app 2. Sign in with your Steam credentials 3. Tap the menu → Steam Guard → Add Authenticator 4. Save your recovery code in a password manager 5. Check Steam’s current trade status after the 7-day protection period
What changes once the 7 days pass
Steam confirms trades and Market listings through the mobile app instead of holding the items. Steam also notes that signing in from a device it has not seen before normally blocks trading for 7 days, and that this new-device restriction does not apply to accounts that have had the authenticator for at least 7 days.
Removing it costs 15 days
Removing the authenticator lowers account security, so Steam blocks trading and the Community Market for 15 days afterwards. Changing phones without moving the authenticator across first triggers the same 15-day window, so transfer it before wiping the old device.
Security note
Never share screenshots of the recovery code or QR. SteamVaults never asks for your Authenticator codes.
Source: Steam Support, Trading and Market Restrictions.