What does 'Error establishing a database connection' mean?

WordPress could not log in to its database, so it cannot build any page. The content is almost always still there. The usual causes are changed login details after a move or password reset, a database server that is down or overloaded, or damaged tables.

How do I fix 'Error establishing a database connection' in WordPress?

Back up the files, then compare DB_NAME, DB_USER, DB_PASSWORD and DB_HOST in wp-config.php with the database listed in your host's control panel and correct any that differ. If /wp-admin says the tables need repair, use WP_ALLOW_REPAIR and /wp-admin/maint/repair.php, then remove the line. If the host reports a database outage, the fix is on their side.

Should I reinstall WordPress or restore a backup?

No, not first. The database is the site, so a reinstall does not bring it back, and restoring an old backup loses everything since then. Rule out the login details and the host's server first.

More fixes

"Error establishing a database connection"

Every WordPress page is built from a database: your pages, posts, orders and settings all live there. This message means WordPress could not log in to that database, so it has nothing to show. Your content is almost always still there. The cause is usually one of three things: the login details changed, the database server is down or overloaded, or some tables are damaged. Below is a rebuilt example (not a real client), then how to tell which cause you have and the safe order of steps.

What visitors see

yourbusiness.com

What the checks found

First: which of the three is it?

Did anything change in the last day? A move to a new host, a new hosting plan, or a password reset on the hosting account all point to the login details.
Open yourbusiness.com/wp-admin. If it says "One or more database tables are unavailable. The database may need to be repaired", the login works and some tables are damaged. If it shows the same connection error, keep going.
Look at your host's status page and its database tool (usually phpMyAdmin in the control panel). If the host reports a database outage, or the database tool itself will not open, the server is down or overloaded and the fix is on their side. If other sites on the same account are down too, it is almost certainly this.

The safe order of steps

Back up the files through the host's file manager or SFTP before changing anything. Most hosts also keep their own daily database backups; note the newest one, but do not restore it yet.
Compare the four login lines. Open wp-config.php and read DB_NAME, DB_USER, DB_PASSWORD and DB_HOST. Compare them with the database and user listed in the host's control panel. A move to a new host very often leaves an old DB_HOST or database name behind; some hosts use a server name rather than localhost.
Reset the database user's password in the control panel if you are unsure of it, and paste the new one into DB_PASSWORD. Check that the user is still attached to the database with all privileges; a move can drop that link.
Repair only if WordPress asks for it. Add define('WP_ALLOW_REPAIR', true); to wp-config.php, open /wp-admin/maint/repair.php, run Repair Database, then remove that line again: the repair page works without a login while it is on.
If the server is overloaded (the error comes and goes, often at busy times), ask the host for the database error log and the account's resource limits. A traffic spike, a bot hammering the site or a runaway plugin query is the usual reason; caching or a bigger plan fixes it, a reinstall does not.
Then test the parts that write to the database: a contact form, a booking or a test order, and log in to the dashboard once.

Common causes and what each one needs

What you see	What it means	Usual fix
Error started right after a move to a new host	`wp-config.php` still names the old database, user or server	Copy the new host's database name, user, password and server into the four lines
Error started after a hosting password or security reset	The database user's password changed and WordPress still uses the old one	Reset the database user's password and update `DB_PASSWORD`
`/wp-admin` says tables are unavailable or need repair	The login works; one or more tables are damaged, often after a crash or a full disk	`WP_ALLOW_REPAIR`, run the repair, remove the line
Error comes and goes; other sites on the account also fail	The database server is down or hitting its limits	Host's status page and support; then caching, bot blocking or a bigger plan
Control panel warns the disk is full or the account is suspended	The database cannot write, or the host stopped it	Clear old backups and logs, or settle the account with the host

What not to do

Do not reinstall WordPress. The database is the site; a fresh install does not bring it back and can overwrite wp-config.php.
Do not restore an old database backup until the login details are ruled out. You would lose every order, booking and form entry since that backup, and the error often stays.
Do not create a new empty database to "get the site back". WordPress will offer to install itself into it, and the site will look brand new.
Do not leave WP_ALLOW_REPAIR switched on afterwards.

If you can open your host's control panel and a file manager, the steps above are usually enough. If the site earns you money every hour it is down, that is what the box below is for.