Platform Version Detection

Vercel CLI will automatically upgrade your deployment to the latest platform version if you import a project or if your project meets certain criteria. In order for this to work, you must:

  • Remove any Dockerfile.
  • Remove the type property from your vercel.json file.
  • Remove the start script from your package.json file.
  • Remove the server.js file from the root of your project.

It is possible to opt out of this behavior by creating a vercel.json file with a version property.

If you are yet to upgrade to the latest platform version, please read our upgrade guide.

What can I deploy with Vercel?

Vercel is best at deploying technologies that can be served over HTTP and distributed through our CDN network:
  • Static websites and static generators (Next.js, React, Vue, Angular, etc)
  • Code that renders HTML on the server-side
  • API endpoints that query databases or web APIs and return dynamic data

In general, most popular technologies and languages already have quickstarts or guides you can start taking advantage of today.

Missing Public Directory

The build step will result in an error if the output directory is missing, empty, or invalid (if it’s actually not a directory). To resolve this error, you can try the following steps:

  • Make sure that the output directory is specified correctly in project settings. Here’s the documentation.
  • If the output directory is correct, double check the Build Command (documentation) or the root directory (documentation).
  • Try running the Build Command locally and make sure that the files are correctly generated in the specified output directory.

Missing Build Script

Note: This is only relevant if you’re using Vercel CLI 16.7.3 or older.

If your project contains a package.json file, no api directory, and no vercel.json configuration, it is expected to provide a build script that performs a static build of your frontend and outputs it to a public directory at the root of your project.

When properly configured, your package.json file would look similar to this:

  "scripts": {
    "build": "[my-framework] build --output public"

An example build script in a package.json file that specifies the output directory.

Once you have defined the build script, this error will disappear. Furthermore, it will not be displayed if you are using package.json purely to provide dependencies for your Serverless Functions located inside the api directory.

Broken Preview Deployment Suffix

The Preview Deployment Suffix feature (available optionally on the "General" team settings page) allows for replacing the suffix of every freshly created deployment with a custom domain of your choice.

In order for this feature to function properly, the custom domain you configured must be:

  • Active (not deleted)
  • Available within the team that enabled the Preview Deployment Suffix
  • Backed by an active wildcard certificate

The easiest way to satisfy all of these constraints is to ensure the domain is also added to a project located within the same team. This project would ideally contain a single index.html that would display when someone visits the bare domain.

Maximum Team Member Requests

No more than 10 requests of users wanting to join a team can be open at the same time. In order to allow for more requests, the existing ones have to be approved or declined by an owner of the team.

This ensures the list always remains managable and protected against spam.

Inviting Users to Team Who Requested Access

If a user already requested access to a team, it's not possible to invite them. Instead, their request must be approved by an owner of the team in order for the user to gain acess.

This ensures no requests are accidentally accepted.

Blocked Scopes

A Personal Account or Team on Vercel might be blocked if it violates our Fair Use Policy or Terms of Service.

Blocked Personal Accounts or Teams cannot create new Deployments, or be invited to new Teams. Please contact Vercel Support if you need help.

Unused Build & Development Settings

A Project has several settings that can be found in the dashboard. One of those sections is called "Build & Development Settings" and is used to change the way a Project is built.

However, the Build & Development Settings are only applied to zero-configuration Deployments.

If a Deployment defines the builds configuration property, the Build & Development Settings are ignored.

Invalid Route Source Pattern

The source property follows the syntax from path-to-regexp, not the RegExp syntax.

For example, negative lookaheads must be wrapped in a group.


  "source": "/feedback/(?!general)",
  "destination": "/api/feedback/general"


  "source": "/feedback/((?!general).*)",
  "destination": "/api/feedback/general"

Invalid Route Destination Segment

The source property follows the syntax from path-to-regexp.

This means that a colon (:) defines the start of a named segment parameter.

A named segment parameter defined in the destination property must also be defined in the source property.


  "source": "/feedback/:type",
  "destination": "/api/feedback/:id"


  "source": "/feedback/:id",
  "destination": "/api/feedback/:id"

Failed to Install Dependencies in Development

When running the vercel dev command, you may experience an npm install error. This happens when npm is invoked to install Runtimes that are defined in your vercel.json file.

npm install may fail if:

  • npm is not installed (retrieve it from here)
  • Your internet connection is unavailable
  • The Runtime that is defined in your configuration is not published to the npm registry

Please double-check that the name and version of the Runtime you are requesting is correct.

Mixed Routing Properties

If you have rewrites, redirects, headers, cleanUrls or trailingSlash defined in your configuration file, then routes cannot be defined.

This is a necessary limitation because routes is a lower-level primitive that contains all of the other types. Therefore, it cannot be merged safely with the new properties.

See the Advanced Routing section for examples of routes compared to the new properties.

Conflicting Configuration Files

For backwards compatability purposes, there are two naming conventions for configuration files used by Vercel CLI (for example vercel.json and now.json). Both naming conventions are supported, however only one may be defined at a time. The CLI will output an error message if both naming conventions are used at the same time.

These conflicting configuration errors occur if:

  • Both vercel.json and now.json exist in your project.
    Solution: Delete the now.json file.
  • Both .vercel and .now directories exist in your project.
    Solution: Delete the .now directory.
  • Both .vercelignore and .nowignore files exist in your project.
    Solution: Delete the .nowignore file.
  • Environment Variables that begin with VERCEL_ have a conflicting Environment Variable that begins with NOW_.
    Solution: Only define the VERCEL_ prefixed Environment Variable.

Conflicting "functions" and "builds" Configuration

There are two different ways to configure Serverless Functions in your project: functions or builds. However, only one of them may be used at a time - they cannot be used in conjuction.

For most cases, it is recommended to use the functions property because it supports more features, such as:

  • Allows configuration of the amount of memory that the Serverless Function is provided with.
  • More reliable because it requires a specific npm package version for the runtime property.
  • Supports "clean URLs" by default, which means that the Serverless Functions are automatically accessible without their file extension in the URL.

However, the builds property will remain supported for backwards compatibility purposes.

Unsupported Functions Configuration with Next.js

When using Next.js, only memory and maxDuration can be configured within the functions property. Next.js automatically handles the other configuration values for you.

Deploying Serverless Functions to Multiple Regions

It's possible to deploy Serverless Functions to multiple regions, but it's restricted to the Enterprise plan for Teams.

On the Pro plan, the limitation has been around since the launch of the current pricing model but was applied on July 10, 2020. For Projects created on or after the date, it's no longer possible to deploy to multiple regions.

To select a single suitable region for your Serverless Functions, please read our guide.

Unmatched Function Pattern

The functions property uses a glob pattern for each key. This pattern must match Serverless Function source files within the api directory.

If you are using Next.js, Serverless Functions source files can be created in the following:

Additionally, if you'd like to use a Serverless Function that isn't written with Node.js in combination with Next.js, you can place it in the api directory (provided by the platform), since pages/api (provided by Next.js) only supports JavaScript.

Not Allowed

  "functions": {
    "users/**/*.js": {
      "maxDuration": 30


  "functions": {
    "api/users/**/*.js": {
      "maxDuration": 30

Allowed (Next.js)

  "functions": {
    "pages/api/users/**/*.js": {
      "maxDuration": 30

Cannot Load Project Settings

If the Project configuration in .vercel belongs to a Team you are not a member of, attempting to deploy the Project will result in an error.

This may happen if you clone a Git repository that includes the .vercel directory, or you are logged in to the wrong Vercel Account.

To fix it, remove the .vercel directory and deploy to link the Project again by running these commands.

On macOS and Linux:

rm -rf .vercel

On Windows:

rmdir /s /q .vercel

Project Name Validation

Project names can only consist of up to 100 alphanumeric lowercase characters. Hyphens can be used in between the name, but never at the start or end.

Repository Connection Limitation

The amount of Vercel Projects that can be connected with the same Git repository is limited depending on your plan.

If you have reached the limitation and would like to connect a new Project to the repository, you will need to disconnect an existing Project from the same Git repository.

To increase this limit, please contact our Sales Team.

Bypassing Password Protection Programmatically

When Password Protection is enabled on your Project, you can bypass the protection programmatically with the following steps:

  • Send a POST request to your Deployment with the password in the request body (_vercel_password=<password>).
  • Parse the Set-Cookie response header and extract the cookie _vercel_jwt from the response.
  • Set the cookie to the Cookie request header when you access the Deployment.

Example Request

cookie="$(curl -s -D - -o /dev/null -X POST -d "_vercel_password=<password>" | grep -i Set-Cookie | grep _vercel_jwt | awk {'print $2'})"
curl -H "Cookie: $cookie"

These steps are required for every URL and cookie values cannot be shared across Deployments.

Domain Verification via CLI

It is no longer necessary to verify your ownership of a Domain using the vercel domains verify command provided by Vercel CLI.

Instead, it's now only necessary for you to point the Domain to Vercel by configuring our nameservers or a DNS Record. You can learn more about what to do exactly for your Domain by running vercel domains inspect <domain>, where <domain> is the Domain you're interested in.

Alternatively, if you already added it to a Project, read this section.

Leaving The Team

You can't leave a team if you are the last remaining owner or the last confirmed member. In order to leave it, you first have to designate a different confirmed member to be an owner of the team.

If you are the only remaining member, you should delete the team instead.

Git Default Ignore List

Deployments created using Vercel CLI will automatically ignore several files for security and performance reasons.

However, these files are not ignored for deployments created using the Git Integration and a warning is printed instead. This is because .gitignore determines which files should be ignored.

If the file was intentionally committed to Git, you can ignore the warning.

If the file was accidentally committed to Git, you can remove it using the following commands:

git rm file.txt                   # remove the file
echo 'file.txt' >> .gitignore     # append file to .gitignore
git add .gitignore                # stage the change
git commit -m "Removed file.txt"  # commit the change
git push                          # deploy the change

GitHub App Installation Not Found

In some cases, signing up with GitHub fails due to GitHub's database inconsistencies.

When you connected your Personal Vercel Account with your GitHub account, the Vercel GitHub App was installed on your GitHub account and then GitHub notified Vercel that the app was successfully installed.

However, Vercel was unable to retrieve the app installation from GitHub, which made it appear as if the Vercel GitHub App was never installed.

In order to solve this issue, please wait a minute and try connecting to GitHub again. If you are still unable to connect, please contact GitHub Support to determine why the Vercel GitHub App was not able to be installed.

Setting Production Branch as Preview

You can only assign non-Production branches to your project's Preview domains. The Production branch must be assigned to a Production environment domain.

Production Deployment cannot be redeployed

You cannot redeploy a Production Deployment if a more recent one exists.

The reason is that redeploying an old Production Deployment would result in overwriting the most recent source code you have deployed to Production.

To force an explicit overwrite of the current Production Deployment, click "Promote to Production" instead.

SSL Certificate Deletion Denied

Certain SSL certificates associated with your Vercel account (i.e. wildcard certificates for your project's staging domain) are automatically generated by the Vercel platform.

Because these certificates are managed by the Vercel platform, they cannot be manually deleted on the Vercel Dashboard nor via the CLI.

Custom SSL certificates may be uploaded to your account, which are allowed to be manually deleted.

Last Edited on August 27th 2020