Can I use Tumblr two-factor authentication without a phone?

Yes. Tumblr only needs an authenticator app that produces single-use six-digit codes; it does not care what device runs it. The Authenticator extension produces them in Chrome on your computer and can read the QR code straight off the Tumblr settings page.

Do the Tumblr apps ask for the code too?

Yes. Once two-factor authentication is on, you sign in as usual — on the web or in the app — and enter the code from your authenticator when Tumblr asks for it. On a phone, open the extension’s icon in Chrome on your computer and type the code it shows.

What if I lose access to my authenticator?

Sign in with one of your backup codes, then turn two-factor authentication off and on again in the Security section to set it up anew — Tumblr makes you go through the whole setup again. Its help page describes no other way back, so generate the backup codes now and keep the extension’s automatic backups on.

Why does Tumblr say my code is wrong?

Usually the computer clock is off by a minute or more. Turn on automatic date and time and try the next code. If it still fails, the account may have been added from an old QR code — remove it from the extension and set two-factor authentication up again.

Tumblr Authenticator App — Turn On Two-Factor Authentication

A Tumblr account holds every blog you run under it, years of posts, drafts and messages — and a hijacked account is used to post spam and scam links to your followers. Tumblr says it “strongly” recommends two-factor authentication: with it on, a stolen password alone no longer signs anyone in, because Tumblr also asks for the code from your authenticator app.

Turn on two-factor authentication on Tumblr

Tumblr asks for your account password during setup, and its codes come from an authenticator app only — so have the extension installed before you flip the switch. In the Tumblr apps the same setting is behind the account icon → gear icon → “General settings” (iOS) or “Account settings” (Android).

Sign in at tumblr.com on your computer.
Click “Settings” on the left — or go straight to your account settings at tumblr.com/settings/account.
In the “Security” section, turn on “Two-factor Authentication”.
Enter your Tumblr password and follow the steps to generate a code.
When Tumblr shows a QR code, leave it on the screen and add it to the extension as described below — then enter the six-digit code from the extension to finish.

Tumblr’s own instructions

Add Tumblr to Authenticator

Install 2FA Authenticator from the Chrome Web Store and pin it to the toolbar, so its icon is one click away.
Leave the Tumblr page with the QR code open. Click the Authenticator icon, then “Add Account” → “QR Code” → “Scan QR from screen”.
The account appears in the list with a six-digit code that changes every 30 seconds. Rename it if you like — the name is only for you.
Go back to Tumblr and type the current code into the confirmation field. If it is about to expire, wait for the next one.
Tumblr confirms that two-factor authentication is on. From now on it will ask for a code when you sign in — click the extension icon and copy it.

No QR code, or it will not scan? Look for the option to enter a key manually on Tumblr’s setup screen, copy the key, and add it in the extension with “Add Account” → “Manual” → “Secret Key”.

Get 2FA Authenticator for Chrome — free

Generate your Tumblr backup codes

In the same “Security” section, click “Generate backup codes”, enter your password and click “Check Password”. Tumblr shows ten backup codes: copy them somewhere other than this computer, or print them with “Print Codes”. When you cannot reach your authenticator, a backup code signs you in instead.

The code is not accepted?

Almost always the computer’s clock. The codes are calculated from the current time, so a clock that is a minute off produces codes that look right and are refused. Turn on automatic date and time in your system settings — step-by-step for Windows, macOS and Linux.

If the clock is right, check the key itself: paste it into the TOTP code generator and compare the code with the one in the extension. If they differ, the key was copied wrong — add the account again.

Questions

Can I use Tumblr two-factor authentication without a phone?: Yes. Tumblr only needs an authenticator app that produces single-use six-digit codes; it does not care what device runs it. The Authenticator extension produces them in Chrome on your computer and can read the QR code straight off the Tumblr settings page.
Do the Tumblr apps ask for the code too?: Yes. Once two-factor authentication is on, you sign in as usual — on the web or in the app — and enter the code from your authenticator when Tumblr asks for it. On a phone, open the extension’s icon in Chrome on your computer and type the code it shows.
What if I lose access to my authenticator?: Sign in with one of your backup codes, then turn two-factor authentication off and on again in the Security section to set it up anew — Tumblr makes you go through the whole setup again. Its help page describes no other way back, so generate the backup codes now and keep the extension’s automatic backups on.
Why does Tumblr say my code is wrong?: Usually the computer clock is off by a minute or more. Turn on automatic date and time and try the next code. If it still fails, the account may have been added from an old QR code — remove it from the extension and set two-factor authentication up again.

Your codes, one click from the login page

Authenticator keeps your 2FA codes in the browser, on your device only — free to use, open source, no account and no phone needed. Local backups and optional password protection come built in.