ongoing by Tim Bray · XML and JSON in 2026

XML and JSON in 2026

The best thing about long-lived incumbent technologies like JSON and XML<br>is that nobody really has to think about them much any more. Except for, I do occasionally, because<br>while I’m not the inventor of either, my<br>name’s on the front of both official specifications. Hey, it’s JSON’s 25th birthday, what a run!<br>And what ever happened to XML? Let’s shake off the dust and have a look.

JSONiana ·<br>RFC 8259 is now nine years old and, like all the RFCs, is<br>immutable. And, as is usually the case, a<br>list of errata has built up over the years.

Until a few days ago, many of the errata apparently hadn’t ever been looked at for a period<br>measured in years. Now they’ve all been rejected or accepted. Despite a couple having been marked “Held for Document Update”,<br>nobody is interested in writing a superseding RFC. There are already enough other JSON specs<br>[1][2]<br>but fortunately they all say the same thing.

Which is to say, JSON is what it is and will never be improved or changed in any way. Among other things, there are literally<br>billions of instances of JSON-reading software out there, most of them embedded in dumb low-rent devices that will never be<br>updated.

Granted, it’s irritating that JSON doesn’t have comments (ProTip: Add a “comment” field to your messages) and makes it<br>hard to get the commas right and doesn’t distinguish between the different flavors of numbers and doesn’t have date/time literals and<br>allows junk Unicode. Not gonna be fixed. Which is OK because<br>empirically, it’s good enough. Probably a few megabytes of JSON will have flowed back and forth between your phone or computer<br>and the Net while you’ve been reading this.

Of course, there’s YAML and TOML and COSE and Thrift and Avro and Protobufs and Markdown and more. Maybe for your app one of<br>them is a better choice than JSON.

Oh wait, I forgot, there is a new thing:<br>Work is under way to write an RFC specifying JSON Schema,<br>which is quite widely used but not well specified. Good luck to the people working on that; I’m not one of them.

The best thing about JSON is nobody really has to think about it any more.

XMLitude ·<br>Last month, on the “xml-dev” mailing list,<br>Elliotte Rusty Harold remarked, on the subject of XML<br>generally: “Count me as one<br>of the people who thinks it’s mostly obsolete and ultimately a failed experiment. People don’t want or need markup<br>that’s designed to make documents easier for computers to read but harder for humans to write.”

I replied and here’s an expanded version of what I wrote:

Irrespective of the current uptake, and seen as an experiment, XML has been<br>a success. It proved that:

You can have a data interchange format that is radically independent<br>of your computer architecture, operating system, programming language, and<br>application.

The only sane text standard for modern computing is Unicode, which in<br>practice is affordable and reasonably straightforward to use.

Prior to 1996, neither of these things were widely believed. The only<br>“interoperable” data format was ASN.1, which is horrible and lacked quality<br>software support. The resistance to Unicode was significant and<br>widespread, and adoption was disappointing. Today, #1 and #2 above are the<br>(low) bar to entry for any data packaging technology.

As for current use, I guess “office" document formats are XML for the long<br>haul<br>[3]<br>[4], but relatively few developers ever have to<br>look inside them (thank goodness). XML remains a de-facto standard for text-oriented humanities computing<br>[5], and for<br>legislative data processing [6][7][8].<br>At one point it dominated things like<br>aircraft maintenance manuals, don’t know if that’s still true. RSS and Atom<br>aren’t what they once were, but are far from gone; they’re how I drive my own personal news-reading.<br>Then of course there’s<br>EPUB; do you read books on screens?<br>And are<br>XBRL and<br>UBL still things?

It is true that there are few-to-no other new applications that I know<br>of that have much reliance on XML.

Eh, it’s OK, it had a good run and moved the needle. It’ll keep a few<br>folks employed for the foreseeable future.

Like JSON, the best thing about XML is nobody has to think about it any more. Oops, if you got here I guess you just<br>did. Sorry bout that.

Updated: 2026/06/02

Contributions

Comment feed for ongoing:<br>From: Yannis (Jun 02 2026, at 10:43)<br>Great post, I've long wanted your thoughts on this actually and good to see you are at peace with XML's relative decline. I do think it was misapplied, and that an edge-labelled graph (which JSON is closer to) is a better representation for most things in the world.<br>I would love to see the post-mortem on the xml-dev mailing list if you would be able to link that. Couldn't find it from a web search.

[link]

ongoing

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June 01, 2026<br>· Technology (90 fragments)

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By Tim Bray.

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