Release notes are the dated, public record a software vendor publishes to say what changed when a new version of its product shipped. A typical entry names the version, gives a date and sorts the changes into categories: new features, altered behaviour, bug fixes, deprecations and, most consequentially, breaking changes that will stop existing code or workflows from working. They exist because the people who depend on a product, whether developers calling an application programming interface (API) or marketers running campaigns through an interface, cannot see inside the vendor's codebase. The release note is the vendor's account of what moved.

In advertising technology the documents carry unusual weight. Budgets are committed against features that may be withdrawn, and the code connecting an agency's tools to Google, Meta or Amazon fails if a field disappears. For trade publications, release notes are also a primary source: a dated statement, in the vendor's own words, of what was shipped and when.

How a release note is built

Most vendors in advertising now follow a broadly similar structure, borrowed from open-source software. The version identifier comes first. Many projects use Semantic Versioning (SemVer), a scheme drafted by Tom Preston-Werner, a co-founder of GitHub, in which a number of the form MAJOR.MINOR.PATCH signals the kind of change. According to the SemVer specification, the major number rises for "incompatible API changes", the minor number for functionality added "in a backward compatible manner" and the patch number for backward compatible bug fixes.

The change categories come next. Keep a Changelog, a convention created by Olivier Lacan, defines six types: Added, Changed, Deprecated, Removed, Fixed and Security. It also recommends an Unreleased section at the top for changes not yet shipped, and a YANKED marker for versions withdrawn because of a serious bug, with the instruction "List it; do not hide it."

Advertising platforms adapt the pattern. The Google Ads API release notes, as of October 2026, are organised by major version and then by minor version, newest first. Each major version carries two tables: one for breaking changes, with columns for the initial state, the new state, the type of change and implementation guidance, and one for non-breaking features labelled as new fields, new enum values, new resources, new metrics or behaviour changes. Entries are grouped by area, such as Assets, Campaigns, Conversions, Reports and Targeting. Google separated breaking changes from non-breaking updates in June 2026, when v24.2 shipped on June 24, and added a separate guide for feature deprecations and "unversioned changes".

The interface-facing equivalent looks different. Google Ad Manager's "What's new" page, according to the Help Center, is "usually published every other Monday" and sorts items under Manage inventory, Traffic and deliver ads, Report and optimize, and Coming soon. Amazon Ads publishes dated, product-specific release notes that track beta-to-general-availability transitions and deprecated endpoints, such as the marketing mix modelling API reaching general availability in 14 countries on May 1, 2026.

Who writes them and who reads them

On the sell side of the relationship, product and developer relations teams write the notes, often alongside a blog post, updated client libraries (the vendor-maintained code packages that wrap an API) and a migration guide. On the buy side, engineers maintaining integrations read the breaking-change tables, campaign managers read interface notes to learn what settings appeared or vanished, and trade reporters read both to establish dates.

The schedule behind the notes matters as much as their content. Google announced on September 4, 2025 that the Google Ads API would move to monthly releases from January 2026, with four major versions a year instead of three and every other month taken by a minor version described as non-breaking. Each major version is supported for one year, after which it reaches its sunset and stops responding. In practice that produced v24 on April 22, 2026, whose breaking removals included several keyword forecasting fields, then v24.1 on May 13, then v25 on July 22 and v25.1 on August 19, which Google called a "drop-in upgrade for v25".

Open-source advertising code moves faster. Prebid.js, the most widely used header bidding library, published 55 versions to the npm package registry during 2025, counting patches, according to the registry's timestamps. Version 11.0.0 appeared on March 12, 2026, and 11.41.0 on October 8, 2026.

Origin and evolution

Change logs are older than hosted software. The GNU Coding Standards describe a file "normally called ChangeLog" intended so that "people investigating bugs in the future will know about the changes that might have introduced the bug". That is an engineer's record; release notes as a curated public document grew with commercial software and, later, hosted platforms that change without any customer installing anything.

Two conventions formalised the modern shape. SemVer gave version numbers a meaning; its current text is version 2.0.0. Keep a Changelog published version 0.0.1 on May 31, 2014, reached 1.0.0 on June 20, 2017 and 1.1.0 on February 15, 2019. Version 2.0.0, released on June 7, 2026, kept the six change types and added guidance distinguishing a changelog from release notes.

Advertising standards bodies followed the same path. Prebid.js 1.0 was announced on December 13, 2017 with support for native, video and banner units. IAB Tech Lab released OpenRTB 3.0 for a 60-day public comment on July 31, 2018. For OpenRTB 2.6 the organisation switched to dated monthly updates labelled by year and month, such as 2.6-202211, and the specification states that, from that update onward, the version number "is only incremented on breaking changes". From 2.6-202303 its change log moved to GitHub Releases. On September 14, 2026, IAB Tech Lab said Markdown on GitHub would replace PDF as the source of truth, with numbered versions becoming tags. Barnaby Edwards, its senior director of product marketing, wrote that "the static nature of the PDF has become a bottleneck rather than a benefit."

Meta added a twist to versioned releases. From May 2024 its Marketing API began automatically upgrading calls to deprecated versions where the next version did not affect the endpoint, flagging them with an X-Ad-Api-Version-Warning header.

Why they matter for marketers

Release notes are frequently the only advance warning of lost capability. When Meta's Graph API v26.0 arrived on July 29, 2026, it blocked 47 commerce order management endpoints with no replacement and removed the Instagram Explore Feed placement, with most restrictions extending to every supported version on October 27, 2026. Microsoft Advertising set out its plan on April 1, 2026 to retire its SOAP API: new features only through REST from October 1, 2026, and full deprecation on January 31, 2027. Agency and vendor tools break on those dates unless someone has read the notes.

For PPC Land, a release note anchors reporting. It supplies a date, a version and the vendor's own description, which can then be tested against what advertisers actually see.

Limitations and disputes

The central weakness is that release notes record what a vendor chooses to disclose. Several categories of change routinely bypass them.

Silent documentation edits are the most common. Google expanded ads in AI Overviews to 11 more countries on December 19, 2025 without an announcement; the change surfaced through an edited help page. A Business Profile metric was added to documentation on March 25, 2026 and spotted by a product expert. The GA4 Measurement Protocol was placed in maintenance mode through a banner on a reference page, with no publicly associated date.

Staggered rollouts are a second problem. A note may say a feature launched while many accounts do not have it. Target CPC bidding for Demand Gen began appearing in select accounts in June 2025 without an official announcement. Allowlists create a related gap: v25.1's lift measurement resources were documented for everyone but usable only by allowlisted accounts.

Unversioned changes sit outside the version scheme entirely. Google's own deprecations page tracks changes that apply regardless of API version, such as the end of new call-only ads on January 1, 2026.

Scope disputes arise when the documented change and its practical effect diverge. After Google announced a change to target-based bid strategies effective August 17, 2026, Ginny Marvin, Google's Ads Liaison, denied it amounted to a broader Smart Bidding overhaul, while practitioners including Joey Bidner argued the effect was structural.

Notes can also be thin. Google's October 8, 2026 announcement of Structured Data Files v11 for Display & Video 360 gave no rationale for its changes.

Not the same as

Changelog. Keep a Changelog answers the question directly: "No, although they draw from the same material." A changelog is the complete, chronological source record; release notes are drawn from it and shaped for an announcement.

Patch notes. The term comes from games and consumer software and describes the notes accompanying a single patch, usually fixes and balance changes. In SemVer terms, a patch release should contain only backward compatible fixes, so patch notes cover a narrower slice than release notes.

Product announcement. A launch blog post or keynote describes what a company wants to promote, often weeks before availability. Release notes are meant to record what actually shipped, including removals no vendor would headline.

Recent developments

Google's monthly API cadence, which began with v23 on January 28, 2026, produced its third minor release of v25 on September 23. Google also grouped its advertising developer documentation under one hub on April 6, 2026, though each product kept its own release notes. IAB Tech Lab's GitHub move makes corrections publishable between numbered versions. And Keep a Changelog 2.0.0 now includes guidance on changelogs drafted by large language models, a sign that the documents are increasingly machine-written and machine-read.

Timeline

  • May 31, 2014 - Keep a Changelog publishes version 0.0.1.
  • June 20, 2017 - Keep a Changelog 1.0.0 is released.
  • December 2017 - Prebid.js 1.0 is published to npm on December 7 and announced on December 13.
  • July 31, 2018 - IAB Tech Lab releases OpenRTB 3.0 for a 60-day public comment ending September 24, 2018.
  • February 15, 2019 - Keep a Changelog 1.1.0 is released.
  • 2022 - OpenRTB 2.6-202211 establishes that the version number changes only for breaking changes.
  • 2023 - From 2.6-202303, OpenRTB release notes move to GitHub Releases.
  • May 2024 - Meta begins auto-upgrading Marketing API calls to deprecated versions.
  • September 4, 2025 - Google announces monthly Google Ads API releases from January 2026.
  • January 28, 2026 - Google Ads API v23, the first release under the monthly schedule.
  • March 12, 2026 - Prebid.js 11.0.0 is published.
  • April 1, 2026 - Microsoft Advertising announces the SOAP API retirement timeline.
  • June 7, 2026 - Keep a Changelog 2.0.0 is released.
  • June 24, 2026 - Google Ads API v24.2 ships with release notes separating breaking and non-breaking changes.
  • July 29, 2026 - Meta Graph API v26.0 blocks 47 commerce endpoints.
  • September 14, 2026 - IAB Tech Lab moves its specifications' source of truth from PDF to GitHub.
  • September 23, 2026 - Google Ads API v25.2 is released.
  • October 8, 2026 - Google announces Display & Video 360 SDF v11; Prebid.js 11.41.0 is published.
  • January 31, 2027 - Scheduled full deprecation of the Microsoft Advertising SOAP API.

Summary

Who: Software and platform vendors such as Google, Meta, Amazon and Microsoft, open-source projects such as Prebid.js, and standards bodies such as IAB Tech Lab write them; developers, campaign managers, agencies and trade reporters read them.

What: Dated documents listing what changed in a software release, typically grouped into new features, changes, fixes, deprecations, removals and breaking changes, often keyed to a version number.

When: Engineering change logs long predate the web; conventions such as Semantic Versioning and Keep a Changelog (first published May 31, 2014) shaped the modern form, and advertising platforms moved to faster, more granular release notes through 2025 and 2026.

Where: On developer documentation sites, help centres, developer blogs and GitHub Releases pages, usually alongside migration guides and updated client libraries.

Why: Ad platforms change continuously, and release notes are the vendor's dated account of those changes, although silent edits, staggered rollouts and unversioned changes mean they are an incomplete record.