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To activate WordPress Multisite on a self-hosted WordPress installation, add define( 'WP_ALLOW_MULTISITE', true ); to wp-config.php above the /* That's all, stop editing! */ comment. Refresh the dashboard, open Tools > Network Setup, choose subdomains or subdirectories, enter the network title and administrator email, then paste the generated code into wp-config.php and .htaccess. Log in again to complete the conversion.
The process changes an existing single site into a network, so make a complete database and file backup first. The activation switch only reveals the setup screen; Multisite is not complete until WordPress generates its network configuration and you install both snippets it provides.
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What activating Multisite does
WordPress Multisite lets one WordPress installation manage multiple sites in a network. The sites share the installation and its administrative framework, while each site can have its own address and content. Activation is a configuration change to an existing self-hosted installation, not a separate WordPress download.
There are two distinct phases. First, WP_ALLOW_MULTISITE unlocks the Network Setup screen. Second, that screen creates the network configuration, including the network-level constants and rewrite rules that WordPress displays for your particular installation. Treat the generated instructions as authoritative for the second phase; do not try to recreate them from memory.
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When you convert an existing site, that site is updated as part of the network creation. A backup is therefore a prerequisite rather than an optional precaution.
Check these prerequisites before changing files
- Back up the database and all WordPress files. Keep the backup somewhere separate from the server and verify that you can access it before proceeding.
- Confirm that pretty permalinks work on the current single site. Open several front-end URLs that use your existing permalink structure. Network rewrite rules build on a working single-site setup.
- Deactivate every plugin. Plugins can be reactivated after the network exists. Deactivating them removes a common source of conflicts while WordPress changes the site structure.
- Ensure you can edit both configuration files. You need write access to
wp-config.phpand to the rewrite file WordPress identifies, normally.htaccesson Apache-style hosting. - Record the current configuration. Save a copy of the original files and note the current site URL, permalink setting and active theme. This makes a rollback or comparison possible if a syntax error appears.
- Check server and DNS constraints with your host. A subdomain network normally needs a wildcard DNS record, and support for Multisite can vary between hosting environments. These are host-level requirements, not settings that the WordPress wizard can guarantee.
Do not begin while a deployment, migration or automated update is running. A partially written configuration file can prevent WordPress from loading, whereas a short maintenance window lets you restore the original files if necessary.
Choose subdomains or subdirectories
Network Setup asks how the sites in your network should be addressed. Make this decision before completing the wizard because it determines the URL pattern and the infrastructure you must maintain.
| Network type | Example site address | What it means operationally | Important prerequisite or caveat |
|---|---|---|---|
| Subdomains | store.example.com |
Each site receives a hostname beneath the main domain. This keeps site paths separate and is useful when sites should look like distinct properties. | A wildcard DNS record is normally required so newly created subdomains reach the WordPress installation. Confirm the exact DNS and hosting setup with your provider. |
| Subdirectories | example.com/store/ |
Each site lives below the main domain in its own path. This avoids creating separate hostnames and often simplifies DNS administration. | Directory-style URLs must coexist with the existing site’s permalink structure. Check the generated rewrite rules carefully, especially when converting an established site. |
Choose the model that matches how users will reach the sites, not merely the option that looks shorter. A later change can require URL redirects, DNS work and content adjustments, so settle the address scheme while the network is being created.
Step 1: Back up and deactivate plugins
- Export or otherwise copy the complete WordPress database.
- Copy the WordPress files, including
wp-config.php, themes, plugins and uploads. - Store the copies outside the live document root.
- In the WordPress dashboard, deactivate all plugins. Leave them inactive until the network configuration has been installed and tested.
For an existing site, this backup covers the site that will become the first site in the network. Network creation updates that site; it does not create a disposable test copy.
Step 2: Add the Multisite permission constant
Open the active installation’s wp-config.php in a text editor that preserves plain PHP text. Add this exact line:
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define( 'WP_ALLOW_MULTISITE', true );Place it above the line containing /* That's all, stop editing! */. The position matters because WordPress reads the configuration before it reaches that marker. Do not add the MULTISITE constant at this stage. WordPress supplies the network-level MULTISITE setting in the generated code during the next phase.
Save the file without changing the opening PHP tag, database settings or quotation marks in unrelated lines. A missing semicolon, an accidental character before the opening PHP tag or a duplicated configuration block can produce a PHP error before the dashboard loads.
Step 3: Open Network Setup
- Return to the WordPress dashboard.
- Refresh the page so WordPress rereads
wp-config.php. - Open Tools > Network Setup.
If the menu item appears, the permission constant was recognized. At this point Multisite is not yet active; the screen is the wizard that creates the remaining network configuration.
WordPress dashboard labels can change between major releases. If the current label differs slightly, look for the network-creation screen under the dashboard’s Tools area rather than adding additional constants manually.
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Network Setup asks for the information WordPress needs to describe the network:
- Enter a network title. This is the administrative name for the collection of sites.
- Enter the network administrator email address. Use an address you monitor because it identifies the person responsible for the network.
- Select either subdomains or subdirectories, based on the URL decision above.
- Review the values before submitting the form. Check the domain, path and administrator address character by character.
After you submit the form, WordPress generates configuration text for wp-config.php and rewrite rules for .htaccess. The exact text depends on the domain, path and URL structure of your installation.
Step 5: Install both generated snippets
The wizard displays two separate instruction blocks. Keep the Network Setup page open while editing the files, or copy the instructions into a secure temporary note.
Update wp-config.php
Paste the complete wp-config.php block exactly where WordPress tells you to place it. The block normally includes the network-level settings that turn the installation into Multisite. Do not substitute a remembered example, omit a line, or add MULTISITE earlier in the file yourself.
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Update .htaccess
Replace or insert the rewrite rules in the location indicated by the wizard. The rules must be in the active site’s .htaccess file, not in a similarly named backup or a different document root. Preserve any unrelated directives only when the generated instructions allow it; do not merge two competing WordPress rewrite blocks casually.
The wizard refers to .htaccess for Apache-style setups. Nginx and some managed or one-click hosting environments do not use that file in the same way. If your server does not execute .htaccess, stop and ask the host how it expects WordPress Multisite rewrite rules to be installed rather than pasting the text into an unused file.
Save and validate
- Save both files.
- Check the file permissions and ownership so the web server can read them.
- Load the site in a new browser tab. If PHP reports a syntax error, restore the backup copy, compare the edited file with the generated block and correct the misplaced character.
Step 6: Log in again and confirm completion
Return to the dashboard and log in again when WordPress prompts you. The wizard should return you to Network Setup as the network administrator. That return, together with the presence of network administration controls, indicates that the generated configuration was accepted.
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Check the original site’s front end and several administrative screens before changing anything else. Confirm that:
- The original home page loads at its existing address.
- At least one page and one post open through their normal permalink URLs.
- The dashboard loads without a PHP warning or rewrite error.
- The network administration area is available to the account that completed setup.
Do not interpret a successful login alone as proof that every site URL works. Test the URL pattern you selected: a representative subdomain if you chose subdomains, or a representative path if you chose subdirectories.
After activation: restore functionality carefully
Reactivate plugins in a controlled order
Return plugins one at a time, or in small groups with a clear record of what changed. Visit the front end and dashboard after each group. A plugin that worked on a single site may need network-aware settings or may be incompatible with more than one site.
If a problem appears immediately after a plugin is reactivated, deactivate that plugin again before changing the network files. This isolates an extension conflict from a configuration error.
Review the network identity
Confirm that the network title and administrator email entered in the wizard are correct. These values identify the network in administrative screens and communications; correcting a spelling mistake early avoids confusion as additional sites are added.
Document the URL model
Write down whether the network uses subdomains or subdirectories, the primary domain and the location of the generated rules. Future administrators need this information when adding sites, changing DNS or diagnosing a rewrite failure.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshooting common activation problems
Network Setup does not appear
- Open
wp-config.phpand confirm the constant is spelled exactlyWP_ALLOW_MULTISITE. - Confirm the value is
trueand the line ends with a semicolon. - Make sure it is above
/* That's all, stop editing! */. - Verify that you edited the
wp-config.phpused by the live site, not a copy in another directory. - Refresh the dashboard after saving. The menu is unlocked by this constant; no generated network block exists yet.
The wizard opens but the site fails after the snippets are installed
Compare each edited file with the text WordPress generated. The most frequent recovery path is to restore the original backup, repeat the wizard instructions carefully and paste the entire block into the requested location. Check for an omitted semicolon, an incomplete rewrite block or a file saved outside the active document root.
Pages return 404 errors after conversion
First check that the generated rewrite rules are in the active .htaccess file and that the server reads that file. Then verify that the original site’s pretty permalinks worked before conversion. If the server is Nginx or a managed platform that ignores .htaccess, obtain the provider’s Multisite rewrite procedure; copying Apache rules into an unused file will not fix routing.
Subdomain sites do not resolve
Subdomain networks normally depend on wildcard DNS and corresponding host configuration. Confirm that the wildcard record points to the WordPress installation and that the host permits the requested subdomains. DNS changes can be host- and provider-specific, so use the values and procedure supplied for your domain rather than assuming a universal record.
A plugin breaks the network
Deactivate the last plugin or group you enabled and retest the original site. Keep all plugins inactive while diagnosing file or rewrite problems; otherwise an extension can mask the underlying configuration issue. Reactivate only after the base network loads correctly.
The host does not support the expected setup
Some Nginx configurations, managed WordPress services and one-click installers impose their own Multisite process or do not support conversion of an existing installation. This is host-dependent and cannot be settled from the WordPress dashboard. Ask the provider whether it supports a self-hosted Multisite network, which URL model it permits and where its rewrite rules belong before making further changes.
Important distinctions to keep straight
WP_ALLOW_MULTISITEis the unlock. Adding it reveals Network Setup; it does not by itself create a network.- The generated block creates the network. WordPress determines the network-level constants after you submit the wizard. Do not pre-empt that step by adding
MULTISITEmanually. - The two generated destinations are different. One block belongs in
wp-config.php; the other belongs in the active rewrite file, normally.htaccesson Apache-style hosting. - The URL choice has infrastructure consequences. Subdomains affect DNS and host configuration, while subdirectories affect path and rewrite behavior.
- Existing content is part of the conversion. The current single site is updated into the network, which is why the database and files must be backed up first.
When to postpone activation
Delay the change if you cannot make or restore a complete backup, cannot edit the active configuration files, or have not confirmed how your host handles the selected URL model. Also postpone it while a critical plugin, migration or deployment is running. Multisite is easiest to diagnose when the starting site is stable, plugins are inactive and every generated instruction can be applied exactly once.
Once those conditions are met, the activation sequence is deterministic: unlock Network Setup, select the network URL model, install the generated configuration in both required locations, log in again and test the original site before expanding the network.
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