Limits
Last updated April 21, 2025
Table of Contents
This article is an aggregation of the limits imposed on various components of the Heroku platform.
Limits exist for several reasons. Some exist because of the architecture of the Heroku platform (for example, Heroku stores only the most recent 1500 lines of an app’s log history). Others exist to ensure good platform citizenship (for example, you can’t make more than 4500 Platform API requests per hour).
Many of the limits listed below link to another Dev Center article that provides additional context regarding the limit.
Add-on Attachments
You can attach the same add-on to a maximum of 100 different apps.
API
The Heroku Platform API rate limit is 4500 calls per hour.
Apps
App Names
App names can be a maximum of 30 characters long.
Number of Apps
- An account can have up to 100 apps.
- A Heroku Team can have up to 100 apps.
- An Enterprise Team can have up to 200 apps.
- A Cedar Private Space can have up to 25 apps.
- A Fir Private Space can have up to 200 apps.
Custom Domains
A single app can have up to 1,000 custom domains assigned to it.
Webhooks
You can configure up to 10 independent app webhook subscriptions per app, add-on, or pipeline.
Build
Concurrent Builds
Only verified accounts can run builds of multiple apps across an account concurrently.
Verified users without an established payment history can create up to 10 concurrent builds at one time. Verified users with an established payment history can create up to 300 concurrent builds at one time.
Ensure that you’re using Heroku Pipelines correctly for any nearly identical apps. Instead of building multiple versions of the same app to deploy, use a pipeline to build artifacts once, then promote them to multiple apps in your pipeline.
Git Repos
Users are limited to a rolling window of 75 requests to Heroku Git repos per hour, per app, per user.
The uncompressed size of a checkout of HEAD from the repo, combined with the size of restored submodules, cannot exceed 1 GB.
Slug Size
Your slug size is displayed at the end of a successful compile. The maximum slug size (after compression) is 500 MB; most apps should be far below this limit. Once a slug size reaches 300 MB we will warn about larger slug sizes having the potential to cause longer boot times.
Slug Compilation
Slug compilation is limited to 15 minutes.
Build Resources
Builds have a maximum memory limit of ~12 GB. Builds exceeding the limit receive an Out of Memory error and must adjust their app builds to fit within the memory limit.
OCI Image Size
The maximum size for an OCI Image is 5 G. App builds that produce images over this limit fail.
Dynos
Dyno Memory
Different dyno sizes offer different amounts of maximum RAM, see Technical Specifications by Dyno Size.
Dyno Memory and Restarts
The maximum amount of RAM available to your application depends on the dyno size you use. The dyno manager restarts your dyno and logs an R15 error if the memory usage of a:
eco,basicorstandard-1xdyno reaches 1 GB, two times its quota.standard-2xdyno reaches 2 GB, two times its quota.performance-mdyno reaches 5 GB, two times its quota.performance-ldyno reaches 28 GB, two times its quota.performance-l-ramdyno reaches 36 GB, 1.2 times its quota.performance-xldyno reaches 74 GB, 1.2 times its quota.performance-2xldyno reaches 151 GB, 1.2 times its quota.private-sorshield-sdyno reaches its quota of 1 GB.private-morshield-mdyno reaches its quota of 2.5 GB.private-lorshield-ldyno reaches its quota of 14 GB.private-l-ramorshield-l-ramdyno reaches its quota of 30 GB.private-xlorshield-xldyno reaches its quota of 62 GB.private-2xlorshield-2xldyno reaches its quota of 126 GB.
All dynos for Fir-generation apps get restarted when the memory usage reaches 100% of their quota.
Attached One-Off Dyno Timeout
Connections to one-off dynos close after one hour of inactivity, in both input and output. When the connection closes, the dyno gets sent SIGHUP. This idle timeout helps prevent unintended charges from leaving interactive console sessions open and unused.
Detached One-Off Dyno Timeout
Detached one-off dynos are cycled every 24 hours. As a result, a one-off dyno run for a maximum of 24 hours
Concurrent One-Off Dynos
The following limits exist per app:
- 1 Eco one-off dyno (Eco requires a subscription to the Eco dynos plan)
- Up to 50 concurrent one-off Basic dynos
- Up to 50 concurrent one-off Standard dynos
- Up to 5 concurrent one-off Performance dynos
- Up to 5 concurrent one-off Private dynos
- Up to 5 concurrent one-off Shield dynos
- Up to 255 concurrent one-off Fir dynos
Submit a request to raise this limit for your application.
Spaces
Refer to Private Space Limits.
Config Vars
Config var data, the collection of all keys and values, has a limit of 64 KB per app.
Boot Timeout
The web process in a dyno must bind to its assigned $PORT within 60 seconds.
If your application requires more time to boot, try the boot timeout tool to increase the limit. However, in general, slow boot times make it harder to deploy your application and make recovery from dyno failures slower, so only consider this method as a temporary solution.
Exit Timeout
When a dyno gets killed or restarts, the processes within the dyno have 30 seconds to exit on receiving a SIGTERM. We send a SIGKILL to the process to force an exit after 30 seconds.
Dyno Restart Limits
See Automatic Dyno Restarts and Dyno Crash Restart Policy.
Dyno Scale
The eco and basic dyno types support a maximum of one running dyno per process type. Additionally, applications that use the eco dyno type are limited to a maximum of two concurrently running dynos.
See Dyno Scaling and Process Limits.
Submit a request to raise this limit for your application.
Processes / Threads
The maximum number of processes/threads that can exist in a dyno at any one time depends on [dyno size](dyno-type. See Dyno Scaling and Process Limits.
Enterprise Teams
Membership Limits
Enterprise Team memberships are limited to:
- 25 members for non-enterprise accounts
- 500 members for enterprise accounts
Heroku Postgres
Dataclips Row Limits
Dataclips can return up to 100,000 rows.
Dataclips Data Limits
Dataclips can return up to 100mb of data.
Dataclips Query Limit Timeout
Dataclips queries cancel after 10 minutes.
Basic-, Standard-, Premium-, and Enterprise-Tier Limits
The limits associated with each Postgres plan tier are described in the Choosing the Right Heroku Postgres Plan article.
Credentials Limit
The maximum number of credentials Heroku Postgres supports is 120.
We strongly recommend that you use as few credentials as possible for security and operational reasons. Be sure to track where you use the credentials.
Logs
Log History
Heroku only stores the last 1500 lines of log history for apps. To persist more than 1500 lines, use a logging add-on, create your own syslog drain or add a telemetry drain. There’s no log history for apps in Shield spaces with Private Space Logging enabled, or for Fir-generation apps.
Drains
- You can have up to 5 log drains on any given Cedar-generation app.
- You can have up to 5 telemetry drains on any given Fir-generation app or space.
Line Length
We split lines generated by dynos that exceed 10000 bytes into 10000 byte chunks without extra trailing newlines. Each chunk is a separate log line.
Build, CI and Release Phase
Log output generated by builds, CI runs and release phase are limited to 300 MB. Any output reaching that limit gets truncated from its beginning, in chunks of 150 MB.
Network
Network Bandwidth
Network bandwidth is soft limited at 2TB per app per month.
Router
HTTP Timeouts
HTTP requests have an initial 30 second window for the web process to return response data. It can be either the completed response or some amount of response data to indicate that the process is active. Processes that fail to send response data within the initial 30-second window see an H12 error in their logs.
After the initial response, each byte sent from the server restarts a rolling 55-second window. A similar 55-second window restarts for every byte sent from the client.
If no data is received from the dyno within the 55-second window the connection terminates and an H15 error is logged.
Similarly, if no data is received from the client within the 55 second window, the connectionterminates and an H28 error is logged.
HTTP Response Buffering
Our routers maintains a 1 MB buffer for responses from the dyno per connection.
HTTP Request Buffering
When processing an incoming request, a router sets up an 8 KB receive buffer and begins reading the HTTP request line and request headers. Each of these can be at most 8 KB in length, but together can be more than 8 KB in total. Requests containing a request line or header line longer than 8KB get dropped by the router without being dispatched.
SSH Keys
All accounts may have a maximum of 50 SSH keys associated with their accounts. If you need more than this you should look into using the Build API.