Internet-Draft Non-ASCII in RFCs March 2023
Hoffman Expires 28 September 2023 [Page]
Network Working Group
7997 (if approved)
7322 (if approved)
Intended Status:
P. Hoffman

The Use of Non-ASCII Characters in RFCs


The RFC Series has evolved to allow for the use of non-ASCII characters in RFCs. While English remains the required language of the Series, the encoding of RFCs is now in UTF-8, allowing for a broader range of characters than typically used in the English language. This document describes requirements and guidelines for the RFC Production Center regarding the use of non-ASCII characters in RFCs.

This document updates RFC 7997 to reflect changes in the practices of the RFC series since RFC 7997 was published, and makes further changes based on agreements in the IETF community about what characters are allowed in RFCs.

[ A repository for this draft can be found here. ]

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at

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This Internet-Draft will expire on 28 September 2023.

Table of Contents

1. Introduction

For much of the history of the RFC Series, the character encoding used for RFCs has been ASCII [RFC20]. This was a sensible choice at the time: the language of the Series has always been English, a language that primarily uses ASCII-encoded characters (ignoring for a moment words borrowed from more richly decorated alphabets); and, ASCII is the "lowest common denominator" for character encoding, making cross-platform viewing trivial.

There are limits to ASCII, however, that hinder its continued use as the exclusive character encoding for the Series. At the time of the publication of [RFC7997], the increasing need for easily readable, internationalized content suggested that it is time to allow non-ASCII characters in RFCs where necessary. To support this move away from ASCII, RFCs switched to supporting UTF-8 as the default character encoding and allowed support for a broad range of Unicode characters [UnicodeCurrent].

This document describes the rules under which non-ASCII characters may be used in an RFC. These rules will be applied as the necessary changes are made to submission checking and editorial tools.

This document updates the RFC Style Guide [RFC7322].

The details included in this document are expected to change based on experience gained in publishing new RFCs.

1.1. Acknowledgements

RFC 7997 was written by Heather Flanagan, who was the RFC Series Editor (RSE) at the time of its publication. Getting the IETF community to agree to the changes embodied in RFC 7997 was a difficult task, and it is likely that this current document would be much more difficult to write had RFC 7997 not been worked out first.

The acknowledgements from RFC 7997 are to the members of the IAB i18n program, to the RFC Format Design Team: Nevil Brownlee, Tony Hansen, Joe Hildebrand, Paul Hoffman, Ted Lemon, Julian Reschke, Adam Roach, Alice Russo, Robert Sparks, and Dave Thaler.

This current document was greatly helped by contributions from the RFC Series Working Group (RSWG), including from Brian Carpenter, Carsten Bormann, Eliot Lear, John Levine, and Martin Thomson.

1.2. Changes from RFC 7997

The following is an overview of the changes in this document from RFC 7997:

  • Added the role of the RFC stream approving bodies and the RFC Production Center (RPC) as described in [RFC9280]. All responsibilities that were held by the RFC Editor in RFC 7997 are handled by the RPC. When the RPC has questions about the content of RFCs, the RPC asks the RFC stream approving bodies for input.
  • Removed requirements of marking non-ASCII characters with XML markup. Clarified that person and names with non-Latin characters should have Latin transliterations.
  • Removed the suggestion that character names for non-ASCII characters be included, instead relying on the "U+NNNN" syntax from [BCP137].
  • Added the suggestion that non-ASCII characters generally appear in NFC.
  • The basic requirements in Section 2 were softened to reflect the realities of the variability of search engines and web browsers.
  • Changed Section 3 from "Rules for the Use of Non-ASCII Characters" to "Use of Non-ASCII Characters" because the RPC has used, and should continue to use, their own discretion based on what makes the RFC most useful.
  • Language about the future was changed to the past tense to indicate that RFC 7997 was already implemented. For example, "RFCs will switch" was changed to to "RFCs switched", and so on. Also added more acknowledgement of the use of non-ASCII characters outside the narrow scope that was defined in RFC 7997.
  • Greatly rearranged and simplified the text about person, company, and postal names.

2. Basic Requirements for Non-ASCII Text in RFCs

The following fundamental requirements inform the guidance and examples provided in this document. They are:

3. Use of Non-ASCII Text in RFCs

This section describes the guidelines for the use of non-ASCII characters in an RFC. If the RPC identifies areas where the use of non-ASCII characters in an RFC negatively impacts the readability of the text, they can require that the authors supply alternate text or change the non-ASCII characters to better suit the expected readers of the RFC. When the RPC has questions about the content of RFCs, the RPC asks the RFC stream approving bodies for input.

In general, using the "U+NNNN" syntax from [BCP137] is the suggested way to show Unicode code points as alternate text.

Characters in an RFC will generally appear in Normalization Form C (NFC) as defined in [UnicodeNorm]. If the RFC would be more correct and more understandable with particular characters not in NFC, the RPC can make an exception and use unnormalized text. In such a case, a text note should be included to describe why unnormalized text used.

Non-ASCII text in person, company, and postal names are covered later in Section 3.1.

When the non-ASCII characters are required for correct protocol operation and understanding, the characters' Unicode code points should also appear in the text in the "U+NNNN" syntax, at least on first use in the RFC. [BCP137] describes the pros and cons of different options for identifying Unicode characters and may help authors decide how to represent the non-ASCII characters in their documents.

Where the use of non-ASCII characters is purely part of an example and not otherwise required for correct protocol operation, giving the Unicode equivalent of the non-ASCII characters is not required, but it can improve the readability of the RFC. For example, for text that says "The value can be followed by a monetary symbol such as ¥ or €", the RPC might require that it instead say "The value can be followed by a monetary symbol such as ¥ (U+00A5) or € (U+20AC)".

Use of the actual non-ASCII character (such as common math symbols like √ and ≤) is encouraged so that a reader can more easily see what the character is. This is done without adding the "U+NNNN" syntax.

[ Removed "The use of the Unicode character names like "INCREMENT" in addition to the use of Unicode code points is also encouraged." This text was, in fact, wrong in 7997 because the character name did not match the example. ]

As another example, [RFC7564] says:

However, the problem is made more serious by introducing the full
range of Unicode code points into protocol strings.  For example,
the characters U+13DA U+13A2 U+13B5 U+13AC U+13A2 U+13AC U+13D2 from
the Cherokee block look similar to the ASCII characters
"STPETER" as they might appear when presented using a "creative"
font family.

This could be replaced with:

However, the problem is made more serious by introducing the full
range of Unicode code points into protocol strings.  For example,
the characters "ᏚᎢᎵᎬᎢᎬᏒ" (U+13DA
U+13A2 U+13B5 U+13AC U+13A2 U+13AC U+13D2) from the Cherokee block
look similar to the ASCII characters "STPETER" as they might
appear when presented using a "creative" font family.

Code components may have different requirements for using the "U+NNNN" syntax. The use of the "U+NNNN" syntax in code components is recommended, except within a code component where one must follow the rules of the programming language in which the code is being written.

3.1. Person and Company Identification

[ RFC 7997 was inconsistent in its rules and examples of when names with non-ASCII characters should be spelled out using all-ASCII transliteration. This section is significantly updated to clarify how names with non-ASCII characters should appear in RFCs. ]

Person names and company names appear in several places within an RFC (e.g., the header, Acknowledgements, and References). It is important to note that non-ASCII characters in person and company names are treated differently than other parts of the body of a document. Names are transliterated into Latin characters; non-ASCII characters in other body text are shown with the "U+NNNN" syntax after the character.

When a script outside the ASCII character set is used for an individual name, an author-provided, ASCII-only transliteration can appear immediately after the non-ASCII characters, surrounded by parentheses. The RPC decides on a case-by-case basis whether to include the ASCII-only transliteration.

Names of authors appear at the top of RFCs and in the References section with a first initial (if available) and family name. For example, Qin Wu's name might appear as "吴钦 (Q. Wu)". As another example, Patrik Fältström's name might appear as "P. Fältström (P. Faltstrom)", but the version with non-ASCII Latin characters also might be left just as "P. Fältström".

In the Acknowledgements section, the person's full name is spelled out in full without the first initial, such as "The following people contributed to this document: 吴钦 (Qin Wu), ...".

Postal addresses may be used without additional Unicode character identification.

If an author's email address includes non-ASCII characters and is a valid email address at the time of publication, it may be given without additional Unicode character identification.

3.2. Keywords and Citation Tags

[ Does the WG still want the following restriction? ]

Keywords (as tagged with the <keyword> element in XML) and citation tags (as defined in the anchor attributes of <reference> elements) must contain only ASCII characters.

4. XML Markup

[ This section needs revision after community discussion ]

As described above, use of non-ASCII characters in areas such as email, company name, address, and name is allowed. In order to make it easier for code to identify the appropriate ASCII alternatives, authors must include an "ascii" attribute to their XML markup when an ASCII alternative is required. See [RFC7991] for more detail on how to tag ASCII alternatives.

5. Internationalization Considerations

The ability to use non-ASCII characters in RFCs in a clear and consistent manner improves the ability to describe internationalized protocols and recognizes the diversity of authors. However, the goal of readability overrides the use of non-ASCII characters within the text.

6. Security Considerations

Valid Unicode that matches the expected text must be verified in order to preserve expected behavior and protocol information.

7. References

7.1. Normative References

Klensin, J., "ASCII Escaping of Unicode Characters", BCP 137, RFC 5137, .
Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", RFC 7991, DOI 10.17487/RFC7991, , <>.
Flanagan, H., Ed., "The Use of Non-ASCII Characters in RFCs", RFC 7997, DOI 10.17487/RFC7997, , <>.
Saint-Andre, P., Ed., "RFC Editor Model (Version 3)", RFC 9280, DOI 10.17487/RFC9280, , <>.
The Unicode Consortium, "The Unicode Standard", , <>.

7.2. Informative References

Cerf, V., "ASCII format for network interchange", STD 80, RFC 20, DOI 10.17487/RFC0020, , <>.
Flanagan, H. and S. Ginoza, "RFC Style Guide", RFC 7322, DOI 10.17487/RFC7322, , <>.
Saint-Andre, P. and M. Blanchet, "PRECIS Framework: Preparation, Enforcement, and Comparison of Internationalized Strings in Application Protocols", RFC 7564, DOI 10.17487/RFC7564, , <>.
The Unicode Consortium, "Unicode Standard Annex", , <>.

Author's Address

Paul Hoffman