Changes Announced on September 19, 2025

The following sections cover planned breaking changes in the v34 release, expected in 2026 Q1. These describe changes as we anticipate them being implemented, but due to the flexible nature of software some of these changes may not land or may vary from how they are described in this topic.

Changes in C++

C++ will bump its major version to 7 with the 7.34.0 release. 6.33 will be the final minor version release on 6.x

Removal of Future Macros

The following macros, introduced for staged roll-out of breaking changes, will be removed and their behavior will become the default:

• PROTOBUF_FUTURE_RENAME_ADD_UNUSED_IMPORT
• PROTOBUF_FUTURE_REMOVE_ADD_IGNORE_CRITERIA
• PROTOBUF_FUTURE_STRING_VIEW_DESCRIPTOR_DATABASE
• PROTOBUF_FUTURE_NO_RECURSIVE_MESSAGE_COPY
• PROTOBUF_FUTURE_REMOVE_REPEATED_PTR_FIELD_ARENA_CONSTRUCTOR
• PROTOBUF_FUTURE_REMOVE_MAP_FIELD_ARENA_CONSTRUCTOR
• PROTOBUF_FUTURE_REMOVE_REPEATED_FIELD_ARENA_CONSTRUCTOR

New RepeatedPtrField Layout

RepeatedPtrField will transition to a new internal element layout where elements are stored in contiguous chunks of preallocated memory, similar to std::deque. This results in some changes to copy/move semantics of some APIs, and some UnsafeArena APIs may become functional equivalents of their arena-safe counterparts and be deprecated.

MSB Hardening Check on RepeatedField::Get and RepeatedPtrField::Get

Protobufs will be hardened against OOB errors by adding comprehensive bounds checking to repeated field accesses.

Remove Arena-enabled constructors from Repeated/Map Fields

The RepeatedField(Arena*), RepeatedPtrField(Arena*), and Map(Arena*) constructors will be deleted.

Remove Deprecated APIs

This release will remove the following public runtime APIs, which have been marked deprecated for at least one minor or major release and that are obsolete or replaced.

AddUnusedImportTrackFile() and ClearUnusedImportTrackFiles()

API: AddUnusedImportTrackFile(), ClearUnusedImportTrackFiles()

Replacement: AddDirectInputFile() and ClearDirectInputFiles()

AddIgnoreCriteria from message differencer

PROTOBUF_FUTURE_REMOVE_ADD_IGNORE_CRITERIA was added for the breaking change. This release will remove the macro.

API: AddIgnoreCriteria()

Replacement: Wrap the raw pointer in a unique_ptr.

FieldDescriptor::has_optional_keyword()

API: FieldDescriptor::has_optional_keyword()

Replacement: has_presence()

FieldDescriptor::label()

API: FieldDescriptor::label()

Replacement: is_repeated() or is_required()

FieldDescriptor::is_optional()

API: FieldDescriptor::is_optional()

Replacement: !is_required() && !is_repeated()

UseDeprecatedLegacyJsonFieldConflicts()

API: UseDeprecatedLegacyJsonFieldConflicts()

Replacement: No replacement.

Stricter Name Length Limits

The protobuf compiler will enforce stricter limits on the length of symbol names, such as field names, to prevent potential issues. If the length of any field name is > 2^16, it will generate an error.

Hide Private Generator Headers in CMake

The protoc generator headers will no longer be installed by CMake. This should not affect most users.

[[nodiscard]] on Logically Constant Operations

[[nodiscard]] will be added to several logically constant protobuf APIs where failure to consume the returned value indicates a probable bug. This follows patterns used commonly in the C++ standard library.

Changes in Python

Python will bump its major version to 7 with the 7.34.0 release. 6.33 will be the final minor version release on 6.x

There is no change in the gencode and we will relax the poison pills. No warnings or errors will be raised for old generated files for 7.34.x.

Raise TypeError on Incorrect Type Conversion to Timestamp/Duration

This release will raise a TypeError instead of an AttributeError when converting an incorrect type to a Timestamp or Duration.

Reject bool to enum and int field

This release will reject setting enum or int fields with boolean values. The API will raise an error instead of implicitly converting them.

Remove float_precision from json_format

This release will remove the deprecated float_precision option from the json_format serializer. This option does not exist in other ProtoJSON serializers and has confusing semantics.

Remove float_format/double_format from text_format

This release will remove the deprecated float_format and double_format options from text_format. These options are not available in other proto text format serializers.

Remove Deprecated APIs

This release will remove the following public runtime APIs.

FieldDescriptor.label

API: FieldDescriptor.label

Replacement: Use is_repeated() or is_required().

Changes in PHP

PHP will bump its major version to 5 with the 5.34.0 release. 4.33 will be the final minor version release on 4.x

Remove Deprecated APIs

This release will remove the following public runtime APIs.

FieldDescriptor getLabel

API: FieldDescriptor getLabel

Replacement: isRepeated() or isRequired()

Google\Protobuf\Field_Kind

API: Google\Protobuf\Field_Kind

Replacement: Google\Protobuf\Field\Kind

Google\Protobuf\Field_Cardinality

API: Google\Protobuf\Field_Cardinality

Replacement: Google\Protobuf\Field\Cardinality

Google\Protobuf\Internal\RepeatedField

API: Google\Protobuf\Internal\RepeatedField

Replacement: Google\Protobuf\RepeatedField

JSON Parsing Strictness

The JSON parser will become stricter and reject several cases that were previously accepted. This includes out-of-bound values, non-integer numeric values for integer fields, duplicate oneof fields, and non-string values for string fields. The JSON serializer will also reject Infinity and NaN for number values.

Fix Silent Ignoring of Default Values

The PHP runtime will be fixed to honor default values on scalar fields in proto2 and editions, instead of silently ignoring them.

Type Checking Alignment

Type checking for pure-PHP and upb-PHP implementations will be aligned. Notably, pure-PHP will reject null for string fields, matching the behavior of upb-PHP.

Changes in Objective-C

Objective-C will bump its major version to 5 with the 5.34.0 release. 4.33 will be the final minor version release on 4.x

The nullability annotations for some GPB*Dictionary APIs will be corrected to mark when APIs could return nil. This will result in Swift code getting a Swift Optional<T> and thus becoming a breaking API change. For Objective-C callers, the annotation correction is less likely to have any impact on the source code.

Remove Deprecated APIs

This release will remove the following public runtime APIs.

-[GPBFieldDescriptor optional]

API: -[GPBFieldDescriptor optional]

Replacement: Use !required && fieldType == GPBFieldTypeSingle instead.

Other Changes

The following are additional breaking changes.

Bazel: Remove deprecated ProtoInfo.transitive_imports

The deprecated transitive_imports field in ProtoInfo will be removed. Users should migrate to transitive_sources.

Remove protobuf_allow_msvc flag and continue support Bazel+MSVC

Due to Bazel’s recent improvements on Windows, we now plan to continue to support Bazel+MSVC. The --define=protobuf_allow_msvc flag will be removed.

Languages Without a Major Version Bump

Java, Ruby, C#, Rust, and JRuby will not have a major version bump in this release.