Thank you for helping make AMP better by fixing bugs, adding features or improving the AMP code in some other way!

This document describes the process you will go through to make a change in AMP.

We want to make it as easy as possible to get in small fixes. A fix for a small bug should be as easy as creating a PR with the change, adding/fixing a test, and sending it to a reviewer.

• Agree to the OpenJSF Contributor License Agreement (CLA).
• (optional) If you are fixing a bug and there is an existing GitHub issue, assign it to yourself (if you can) or comment on it to let others know you are working on it. If there is no GitHub issue consider filing one, but for minor fixes your PR description may be enough.
• (optional) Find a guide before you start coding to help you answer questions.
• Follow the parts of the Implementation section that makes sense for your change. There are many parts of the process that you probably won't need to follow for a minor fix--e.g. you may not need to make validator changes or put your change behind an experiment for minor fixes. If in doubt ask your guide or the #contributing channel on Slack.
• When your code is ready to review, find people to review and approve your code.
  • Your code must be reviewed/approved by an Owner for each area your PR affects and a Reviewer. (It is acceptable and common for one person to fulfill both roles.)
    • after your PR is created, a bot will automatically find Owners that can approve your PR and add them to your PR; you may also view the OWNERS file in the directories you change (or their parent directories)
    • choose a Reviewer; it's possible that the Owners that were automatically added by the bot are also Reviewers
  • If the Owner that was automatically added is not a Reviewer, or you want to have someone else review and approve your code add them as reviewers on your PR if you are able to do so, otherwise cc them by adding the line "/cc @username" in your PR description/comment.

If your run into any issues finding a Reviewer/Owner or have any other questions, ping the #contributing channel on Slack.

Significant changes (e.g. new components or significant changes to behavior) require consultation with and approval from knowledgeable members of the community.

If you are making a change to existing behavior, familiarize yourself with AMP's policy on breaking changes.

If you are deprecating/removing a feature, follow the deprecation process instead of this process.

• Before you start coding, find a guide who you can discuss your change with and who can help guide you through the process.
• Agree to the OpenJSF Contributor License Agreement (CLA).
• File an Intent-to-implement (I2I) GitHub issue and cc your guide on it. The I2I should include:
  • A description of the change you plan to implement.
  • If you are integrating a third-party service, provide a link to the third-party's site and product.
  • Details on any data collection or tracking that your change might require.
  • A prototype or mockup (for example, an image, a GIF, or a link to a demo).
• Determine who needs to approve your I2I. Changes that have a significant impact on AMP's behavior or significant new features require the approval from the Approvers Working Group (WG). Work with your guide to determine whether your change is significant enough that it requires approval from the Approvers Working Group and/or any other Working Group.
• Get pre-approval from the Approvers WG if needed. For changes that require approval from the Approvers WG, at least 3 members of the Approvers WG should provide pre-approval on the I2I before significant implementation work proceeds.
• Finalize the design of your change.
  • Familiarize yourself with our Design Principles.
  • Your guide can help you determine if your change requires a design doc and whether it should be brought to a design review.
• Proceed with the implementation of your change.
• For changes that require approval from the Approvers WG, file an Intent-to-ship (I2S) issue. Indicate which experiment is gating your change and a rollout plan. Once this issue is approved by 3 members of the Approvers WG the rollout plan described in the I2S may proceed.

A guide is a member of the AMP community who is knowledgeable about the area you are modifying and who can guide you from the design phase all the way through launch.

A guide is required if you are making a substantial change to AMP, but is optional if you are making smaller changes.

To find a guide:

• The Working Group that is most responsible for the area you are changing may document how to find a guide from that Working Group. If they do not, reach out to the facilitator of the WG (on Slack or by ccing them on your GitHub issue by adding "/cc @username" in the issue body or comment).
• If there is no obvious Working Group responsible for the area you are changing but you know what part of the codebase your change will be in, reach out to one of the people in the OWNERS files for the areas you're changing (on Slack or by ccing them on your GitHub issue).
• If you're still not sure who your guide should be, ask for a guide on Slack in the #contributing channel.
• If you can't find a guide after going through these routes or the guides you find aren't responsive, reach out to mrjoro on Slack or cc him on your GitHub issue/PR.

Once you have found a guide, make sure to @-mention them on any issues / PRs related to your change (e.g. if mrjoro is your guide you can just add "/cc @mrjoro" in the issue/PR body or comment).

• (optional) Join AMP on GitHub. You don't need to wait to be added to the org before you start coding.
• Perform the one-time setup if needed: Set up your GitHub account, install Node, fork repo, track repo, etc.
• Create a working branch.
• Build AMP.
• Write your code.
  • For more substantial changes, multiple smaller PRs are preferable to one large PR. These will be easier to review and can prevent wasted work.
  • Consult these resources for guidance and guidelines:
    • Design: AMP Design Principles
    • JavaScript: Google JavaScript Code Style Guide
    • CSS: Writing CSS For AMP Runtime
    • Creating new components:
      • Instructions and Guidelines for building an AMP component
      • Learn to create your first component in this guide
      • Watch this YouTube video to learn about "Building a new AMP component"
    • Integrating third-party software, embeds, services: Guidelines
    • Accessibility:
      • Web Fundamentals - Accessibility
      • web.dev Lighthouse accessibility audits guide
  • Put your change behind an experiment flag unless it is a minor fix or your reviewer indicates this is not needed.
  • Commit your files.
• Test your changes.
  • A key feature of AMP is performance. All changes will be analyzed for any performance impact; we particularly appreciate changes that make things even faster. Please include any measured performance impact with substantial pull requests.
• Prepare for your code review.
  • For more substantial changes, it's usually preferable to have your code reviewed before you make a significant investment in new tests, examples, etc.
  • Before your final review, make sure your change:
    • Has good test coverage
    • Follows the style and design guidelines
    • Provides good documentation
    • Passes the presubmit checks (no lint and type check errors, tests are passing)
    • Includes validation rules and tests, if relevant
    • Provides an example, if relevant
• Send your code for review.
  • Agree to the Contributor License Agreement if you have not already done so.
  • Pull the latest changes from the amphtml repo and resolve any conflicts.
  • Run the pre push check, which is a tool that helps catch any issues before you submit your code. To enable the git pre-push hook, see enable-git-pre-push.sh.
  • Push your changes
  • Create a Pull Request (PR).
  • Make sure the presubmit checks shown on your PR on GitHub passes (e.g. no lint and type check errors, tests are passing).
  • Add reviewers to your PR that will fulfill the requirements of code review and approval documented in the Code review and approval section. (A bot will automatically assign Owners that can review your code, and your guide can help find Reviewers if needed.)
  • Respond to feedback.
• After your PR has all of the necessary approvals, your code may be merged into the repository by any Collaborator/Reviewer. Your guide will typically handle this; reach out to them if your code is not merged soon after it has been approved.
• To check on your changes and find out when they get into production, read See your changes in production.
• Clean up: After your changes are merged, you can delete your working branch.

AMP is designed to be extensible - it is meant to support “Extended Components” that provide first-class support for additional rich features.

Because Extended Components may have significant impact on AMP performance, security, and usage, Extended Component contributions will be very carefully analyzed and scrutinized.

In particular, we strive to design the overall component set, so that a large number of use cases can be composed from them. Instead of creating a new component it may thus be a better solution to combine existing components to a similar effect.

We have a few additional resources that provide an introduction to contributing extended components:

• "Building an AMP Extension" has a detailed description of how to build an AMP component.
• The "Building a new AMP component" talk at AMP Conf 2017 provides an introduction to contributing AMP components.

For further detail on integrating third-party services (e.g., fonts, embeds, etc.), see our 3p contribution guidelines.

AMP requires all contributors to agree to the OpenJSF Contributor License Agreement in order to protect contributors and users in issues of intellectual property.

To agree to the OpenJSF Contributor License Agreement, visit https://cla-assistant.io/ampproject/amphtml, read through the agreement, and click "Sign in with GitHub to agree."

Alternatively, you also have the option of downloading the Contributor License Agreement from https://individual-cla.openjsf.org, filling it in, signing it, writing in your GitHub handle, and emailing it to operations@openjsf.org. As processing your CLA is done manually, this takes much longer and is therefore not recommended.

All code in AMP must be reviewed and approved before it is merged. Reviewers/Collaborators primarily ensure that the code is correct, efficient and consistent with existing AMP code while Owners primarily provide a domain-specific review of the code.

To be merged, all code must be approved by both:

• At least one Reviewer who is not the author. If the author is a Reviewer, a Collaborator may fulfill this requirement instead.
• At least one Owner for all areas the PR affects, except those areas in which the code author is an Owner.

It is acceptable for one person to fulfill these requirements, e.g. if an Owner who is also a Reviewer approves the PR it may be merged.

We now have a bot that will automatically assign Owners to a PR once it is created, and it is likely at least one of these Owners will also be a Reviewer.

Once the PR has been approved, anyone with commit rights to the repository may merge the PR, including its author.

These guidelines are specific to the amphtml repository. Other ampproject repos may follow the same guidelines or use different guidelines as documented in their docs/contributing.md files.

• Review, approve and merge PRs in the repository for which they are Collaborators.
• Collaborator status is granted to folks who have proven basic familiarity with the respective repository.
• A person may become a Collaborator after 2 merged PRs that are non-trivial (not only fixing typos, not only config changes) and a +1 from 1 current Reviewer. To request becoming a Collaborator file an issue in the repository in which you are requesting to be a Collaborator and cc a Reviewer in that repository.
• The list of Collaborators is maintained in the Collaborators (amphtml) GitHub team.

• Review, approve and merge PRs in the repository for which they are Reviewers.
• Reviewer status is granted to folks who have demonstrated deep familiarity with the code-style and conventions of the respective repository.
• A person may become a Reviewer after 10 merged PRs or 10 high quality reviews of complex PRs and a +1 from 1 current Reviewer. Qualifying PRs must be non-trivial (not only fixing typos, not only config changes) and should have implemented or documented at least 2 new features. To request becoming a Reviewer file an issue in the repository in which you are requesting to be a Reviewer and assign/cc a Reviewer in that repository.
• The list of Reviewers is maintained in the Reviewers (amphtml) GitHub team.

• Review & approve PRs in the area in which they have expertise.
• Requirements to be an Owner:
  • Demonstrated expertise in the area in which they are an Owner.
  • Any GitHub user (including those who are not Reviewers or Collaborators) may be an Owner.
  • When creating a new directory (such as when creating a new AMP extension) the author of the pull request should designate themselves as an Owner of that directory.
  • Owners of an area may approve other Owners at or below their area of expertise following the normal PR process. To request becoming an Owner create a PR adding yourself to the appropriate OWNERS file and assign/cc a current Owner for that directory.
• The list of Owners for a directory can be found in the OWNERS file in the directory or a parent directory.
• Please note that some Owners may be relevant regardless of code location and therefore may include one or more AMP Working Groups, such as the groups for Security & Privacy and Components, which can provide guidance on web accessibility.

We have a well-defined process for handling requests for changes to the experimental/beta, stable, or lts release builds. These changes are known as "cherry-picks".

Note: We do not support cherry-picks into the nightly release channel; in the event of security or privacy issues, a rollback is performed instead.

The bar for getting a cherry-pick into a live release is very high because our goal is to produce high quality launches on a predictable schedule.

Keep in mind that performing a cherry-pick requires a significant amount of work from you and the on-duty engineer and they can take a long time to process.

• In general only fixes for P0 issues may be cherry-picked. P0 issues are those that:
  • cause privacy or security issues
  • cause user data loss
  • break existing AMP web pages in a significant way
  • cause an outage or critical production issue
  • or would otherwise cause a significant harm to AMP's reputation if left unresolved
• Regressions found in the experimental/beta releases that are not P0 may be approved if they can be resolved with a rollback. Fixes other than rollbacks--no matter how simple they may seem--will not be approved because these have the potential to cause cascading problems and delay the release promotion of beta to stable for everyone.

The following outlines the process to request a cherry-pick.

• Ensure there is a bug report filed for the problem, and ensure it is resolved before filing the cherry-pick request.
• Escalate the issue to P0 by attaining consensus from one or more members of the Approvers Working Group (WG) (if you are a member of this working group, you may not count your voice for consensus purposes)
• File the cherry-pick request issue using the Cherry-pick request template. Follow the instructions in the template, providing all the requested data. Make sure you fill out this issue completely or your cherry-pick may not be seen or acted upon.
• Get the necessary approval for your cherry-pick, indicated via comments on the cherry-pick request issue.
  • For cherry-picks into experimental/beta, at least one member of the Approvers WG must approve the cherry-pick/rollback.
  • For cherry-picks into stable/lts at least one member from the Cherry-Pick Approvers group must approve the cherry-pick.
• Once approved, the on-duty engineer handling releases will work with you to ensure the cherry-pick is made.
• Once the cherry-pick is made you are responsible for verifying the cherry-pick fixes the issue and does not cause other issues.

If you are requesting a cherry-pick to fix an issue in production it is likely you will also need a cherry-pick into the experimental/beta releases. Problems cherry-picked in stable could be overridden after promoting beta. The on-duty engineer will help determine if you need to cherry-pick both release channels.

It is possible that a P0 issue gets discovered on Monday or Tuesday, when it was already present in the code-base in the previous week. When that happens, the previous week's nightly release (which is bound to be promoted to experimental/beta on Tuesday morning) will contain the offending code without the fix. In this case, the release on-duty engineer must perform a cherry-pick before promoting last week's nightly to experimental/beta.

Note: While the cherry-pick is performed on top of last week's nightly release, we do not promote that fix to the nightly release channel. This is because the cherry-pick is performed on top of a previous nightly release, not on top of the latest.

If you run into any issues or have any questions when requesting a cherry-pick, please use the AMP Slack #release channel (sign up for Slack).