> over 3 billion people to message securely each and every day.
Whatsapp is a chat application with 3 billion daily active users.
For those of you in the US (where Whatsapp is seldom used), this is a fact worth remembering.
If you want to build products for the rest of the world, you need to know how those users think and breathe - and for 3 billion of them, Whatsapp is how they talk.
> We believe that this is the largest rollout globally of any library written in Rust.
I think that crown currently goes to https://github.com/googlefonts/fontations which is included in Chromium, not sure if it's on all platforms yet. Moreover, the translative dependencies of Fontations (click through https://crates.io/crates/fontations/0.3.0/dependencies) should have an even (slightly) larger install-base.
EDIT: from the quote you can also gather that they don't use https://github.com/signalapp/libsignal
Just for reference, Wamedia ships on the major Meta apps and on iOS, Android, Desktop, and Web platforms.
Just a few more Rust libraries we've shipped in Chromium:
- https://github.com/image-rs/image-png
- https://github.com/webmproject/CrabbyAvif
The 160k → 90k LOC reduction is nice, but the parallel rollout is the more interesting part. Running Rust alongside the C++ version and using differential fuzzing to check equivalence is a lot more realistic than “rewrite and pray.” You get incremental validation with the old system as a fallback. Curious how long they ran both before cutting over.
Binary size is a real concern on the client side. On servers the Rust stdlib overhead usually doesn’t matter, but when you’re shipping to billions of mobile devices, every KB counts. Good to see they invested in build tooling instead of just accepting the bloat.
Did they say anywhere what they did? Rebuilding the stdlib as part of your build can shrink it a lot depending on how much of it you use, but that is still nightly only. Maybe they went no_std or created their own?
They didn't but keep in mind that the app is currently 170MiB. The standard library shouldn't have added more than a few hundred kilobytes. They already likely pay similar costs for c++, but it's more worthwhile as they have a lot more c++ code total.
Also note that if you statically link to the rust std library, lto will excise the majority of it anyways, no need to rebuild it.
The default hello world stripped with one codegen unit and panic=abort was 342kB both nightly and stable. Adding lto dropped it 42kB in stable and 40kB in nightly. Adding build-std and only building core did not reduce it any further in size.
I love how Meta will do anything but prevent phishing and prepaid credit card scams in Whatsapp/Messenger
The hardest part of a rewrite like this is usually maintaining bug-for-bug compatibility with the legacy parser rather than the actual Rust implementation. Most real-world media files are malformed in some way that the C++ code implicitly handled, so if you write a strict parser you end up breaking valid user data. Differential fuzzing seems like the only practical way to map that behavior without manually reviewing millions of edge cases.
It sounds like it's a design goal of this "wamedia" to _not_ maintain bug compatibility with media players.
I suspect it is actually about maintaining permissiveness for malformed inputs rather than keeping security bugs. I ran into this building ingestion for a print-on-demand service where users upload technically broken PDFs that legacy viewers handle fine. If the new parser is stricter than the old one you end up rejecting files that used to work, which is a non-starter for the product.
AI reply?
Not AI. Anyway, the real issue is permissiveness vs strict parsing—real-world files are messy.
> We believe that this is the largest rollout globally of any library written in Rust.
I suppose this is true because there's more phones using WhatsApp than there are say Windows 11 PCs.
Given that WhatsApp uses libsignal, is it safe to assume that they haven't been using the Rust library directly?
WhatsApp doesn't use libsignal, and Android is already pretty Rusty and deployed more than WhatsApp around the world (not just smartphone. Tons of "embedded" use cases also run on custom Android)
WhatsApp was using libsignal (the C version) when I worked on the KaiOS integration in 2017/2018.
>deployed more than WhatsApp
If you count old Android versions before Rust was added.
Like our gym devices that have a full tablet to run a basic application to control weights, talk about wasting money.
It doesn't make sense for that device alone, but the vendor probably supplies all the different equipment in the gym. Using a tablet simplifies their supply chain, deployment, debugging/repair, app update process and simply supports more features. There are probably some connectivity features on the device, for example. When you look at all of that together, it's hard to argue it's wasting money.
It's like complaining about Electron apps. For sure I love small native apps like everyone else. But, if Electron enables a company to ship cross-platform apps and iterate faster, who am I to say no?
(I happen to have seen some of those tablets in diagnostic mode and poked around a bit. These things are much more complicated than you think.)
> Weight equipment should be able to last decades.
"should" or "actually can"? Do you have references to show that's the actual lifespan of the equipment, mechanically?
Once you price in the cost of integration, plastics, ROHS, CE and other regulatory/certifications, the extra cost of an Android tablet which already has a lot of that starts to make sense.
If you also add in the extra ease of things like device management across fleets etc, it becomes a no-brainer for the manufacturer.
And then you get to a cardio unit where you want a completely different set of features and have to start over. Going lean on hardware only makes sense when you push out a very high number of units, when you have to deal with battery constraints or when you just have a lot of intertia, the combination of existing codebase and developer filter skillset.
If you watch "Microsoft is Getting Rusty: A Review of Successes and Challenges" it appears the whole effort is more on the Azure side, and besides some timid adoption like GDI regions, there is a lukewarm adoption of Rust on Windows side, still pretty much a C and C++ feud.
> Two major hurdles were the initial binary size increase due to bringing in the Rust standard library [...].
They don't say what they did about it, do they? Did they just accept it?
I suspect they just use no_std whenever its applicable
https://github.com/facebook/buck2/commit/4a1ccdd36e0de0b69ee...
https://github.com/facebook/buck2/commit/bee72b29bc9b67b59ba...
Turn out if you have strong control over the compiler and linker instrumentations, there are a lot of ways to optimize binary size
Probably yes. It's ~300KB per binary, and it's a one-time cost.
It can be avoided entirely by disabling the standard library, but that's inconvenient, and usually done only when writing for embedded devices.
Usually the problem isn't the size directly, but duplication of Rust dependencies in mixed C++/Rust codebases.
If you end up with a sandwich of build systems (when you have library dependencies like C++ => Rust => C++ => Rust), each Rust/Cargo build bundles its copy of libstd and crates. Then you need to either ensure that the linker can clean that up, or use something like Bazel instead of Cargo to make it see both Rust and C++ deps as part of a single dependency tree.
The size is not fixed. It changes based on how much of the standard library you use. Dynamically linking the standard library is also a valid option in many cases.
Posted elsewhere but The default hello world stripped with one codegen unit and panic=abort was 342kB both nightly and stable. Adding lto dropped it 42kB in stable and 40kB in nightly. Adding build-std and only building core did not reduce it any further in size.
Can it do lto on stdlib even without the nightly build-std flag?
We invested a lot into build system optimizations to bring this number down over time, although we did accept on the order of 200 KiB size overhead initially for the stdlib. We initially launched using a Gradle + CMake + Cargo with static linking of the stdlib and some basic linker optimizations. Transitioning WhatsApp Android to Buck2 has helped tremendously to bring the size down, for instance by improving LTO and getting the latest clang toolchain optimizations. Buck2 also hugely improved build times.
Who knows what they did, but there are things which can be done: https://github.com/johnthagen/min-sized-rust
The whole article a bit watery which is why I read it as a PR rather than technical presentation
Very cool! I'm wondering if Signal is doing something similar? libsignal is implemented in Rust, but I don't know about the other parts.
> "WhatsApp provides default end-to-end encryption for over 3 billion people".
Wasn't there news lately that they can still read your messages somehow?
WhatsApp could exfiltrate messages at the ends. But I assume the trick lies in the word "default". Didn't Skype also default to end-to-end encryption, unless there was a server flag that disabled it for that specific user (I might be fuzzy on the details)
I don't trust un-auditable client applications...
If you want to assure me your e2e is secure, there must be at least two clients implemented by different people, with at least one of them opensource.
Whatsapp used to have this, but lately they have cracked down on third party clients.
Even if they have, this doesn't prevent from turning on a feature flag, or push an experimental build to some users.
If there is a 2nd opensource client written by someone else, you would hope they would raise the alarm when asked to implement "feature flag 437 means send all the crypto keys to the server".
Every encryption is end to end if you're not picky about the ends, or metadata.
Do you trust facebook (excuse me, meta) to not snoop on your messages, and to not share them with the "intelligence" agencies ?
This is not true. The IETF draft is explicit that E2EE means that the message cannot be read by any party other than the sender and the intended receiver. When companies like Meta claim they support E2EE, this is what they claim. There are no tricky semantics or legalese at play here.
> When companies like Meta claim they support E2EE, this is what they claim.
Well, that statement can only resolve to true.
These requests of data collection are perfectly legal. FBI DITU gives an order: give me all chats from *@banana.com and they receive banana.com.
From there, two choices from the perspective of a tech provider:
a) You accept. You get paid.
You can always claim you had been coerced / are a victim, and that everything has been done by the law.
You take the risk to lose over 250K per day (!) in fines, some other court scandals that will come to you, some shady private stuff (what if we learn about your secret jacuzzi ?), harassement of the team, be publicly shamed that you supported terrorists who caused actual death of Americans, etc.
In addition, nobody will know that you are the privacy hero and you are not even sure that the data is not exfiltrated another way.
Yes, we looked carefully and decided we won't enjoy losing 100M USD and go to jail.
The trick is that the identifier / wildcard can be very vague and wide. Or there can be multiple of them, each of them are narrow, but put one of top of the other they are super wide.
To be fair zoom did claim E2EE, with one of the ends being their servers.
It's not entirely accurate to say "any party other than the sender and the intended receiver," since the messaging app running on the user's device can read the messages. Something like "any third party (other than the app vendor)" would be more accurate. Without actually analyze app behavior, it comes down to trusting that the vendor doesn't do anything nefarious.
Oh it's definitely possible. The (dis)incentives tend to be strongly against such secure systems, though.
Technical drafts will tend to get this right, where the communication often breaks down is how it's communicated to users.
Yes, the app could be compromised, or the OS, or the compiler of the app, or of the OS, or the OS of the compiler, or the CPU any of these things run on, etc. etc. None of that is relevant to the definition of E2EE.
Quite impressive, I did not know so many bugs were due to memory access.
To be fair the increased reliability of Rust code over C++ isn't just because of memory errors (out-of-bounds accesses, use-after-free, type confusion, etc). You also get:
* No undefined behaviour (outside `unsafe`, which is quite easy to avoid). In C++ there are many many sources of UB that aren't really memory errors directly, e.g. signed integer overflow or forgetting to `return` from a function.
* A much stronger type system.
Those two things have a really significant impact on reliability.
Rust's "A language empowering everyone..." tagline also helps justify the heavy lifting needed to prevent you shooting yourself in the foot, because we're all able to imagine a hypothetical less experienced programmer who might make a mistake even as we swear that we'd never make it ourselves.
Just like Google’s Rust-in-Android blogs this reads like a PR piece (and in the case of facebook also recruitment piece) with some technical words sprinkled in for effect. The overall communication quality is that of a random startup’s “look what we did” posts.
The interesting aspects, such as how they protect against supply-chain attacks from the dependency-happy rust toolchain or how they integrated the C++ code with the Rust code on so many platforms - a top challenge as they said - remain a mystery.
Would also be interesting to hear how much AI-driven development they used for this project. My hope’s that AI gets really good at Rust so one doesn’t have to directly interact with the unergonomic syntax.
The point of articles like this is to help build credibility for rust adoption. Rust is still not very widely adopted industry wide, and a lot of smaller players only use established technologies that bigger firms have shown works well. Rust is not inevitable, and articles like this are necessary for its future industry adoption.
I had already said it’s a PR piece, you’re merely rephrasing that and making it sound like a good thing.
This and the Google blogs offer zero technical insights and I haven’t learned anything from any of them.
> The interesting aspects, such as how they protect against supply-chain attacks
There are standard techniques to help manage this that apply across languages, there's no reason to reinvent that wheel.
> My hope’s that AI gets really good at Rust so one doesn’t have to directly interact with the unergonomic syntax.
"Unergonomic syntax" is the battle cry of many people resisting learning a new language. AIs have progressed far enough that they can help you in that learning process, though.
The dependency management and complexity/poor ergonomics are the two major technical problems with Rust. Normally the first one’s ignored while the second is downplayed, so it would have been interesting to see what (if anything) Facebook have done about them.
Not only can AIs help, but they can write most if not all the code and spare the human from learning all the intricacies of individual programming languages. Problem is, reports are contradictory on compatibility with Rust. We know they work great with simpler/friendlier languages like Go or Python.
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That's right, Signal (https://kerkour.com/signal-app-rust), Proton (https://kerkour.com/proton-apps-rust), Matrix, Wire and many more are using a share, cross-platform Rust core and a platform-dependent UI layer.
But it's not only the security-critical paths, but also most of the business logic (see the 2 posts above).
I agree with everything you say. But wow, does that comment sound like AI. Probably Grok?
Not saying you are AI, you might just be a heavy user who picked up the same patterns
If it were an old account I might have given them the benefit of the doubt, but they literally just joined to make this comment. There's so many green accounts popping up which reek of AI now, like I've seen ones where all of their comments are almost exactly the same length.
It's a brand new account that reads 100% like a ChatGPT response where the author just swapped out the em dashes for hyphens when posting, knowing it's a common "indicator" people look for.
It's more surprising to me that it seems to have already fooled a bunch of people looking at their replies to you.
I like your AI slop detector, is it part of your consciousness ?
The "is key - ", is a key giveaway.
EDIT to expand the evidence: It's placing unnecessary emphasis on a one off mention in the article (differential fuzzing) and then writes a bunch of bullshit around what it thinks it means (it's wrong, differential fuzzing isn't running them both in parallel during a transition, it's a testing methodology based on inputs/outputs).
Which many people use. Heck, go to Stack Overflow about 10 years back. You will see people using it. It's a style.
TIL I'm an AI
I think it's a giveaway that it's human! A hyphen is incorrect punctuation.
According to British style guides an en-dash would be correct in that usage, and the difference between an en-dash (–) and a hyphen (-) is pretty small. Seems perfectly defensible to me unless you are publishing a book or academic journal
AI is trained on human output, so that's not really a good differentiator.
Cool - now we only need to get selling-you-out-for-profit-Zuckerberg out of WhatsApp to make it really trustworthy.
Let's see how this unwrap()s in production scnr
Oh come on, that was funny. It also highlights a problem with the way people write rust. If your app panics it has a bug. People throw panics in cases that can absolutely happen, a file isn't there or fails to parse, some set of inputs is mutually inconsistent these are things for error checking. Even if the correct way to handle an error you detect is to stop the app, do that instead of panicking. Panics are for things that should be impossible. Ideally they even get optimized out.
The differential fuzzing approach is clever — way safer than a big-bang rewrite. Running both versions in parallel to catch edge cases before switching over is how you actually ship rewrites without breaking production. The 160k to 90k LOC drop is impressive, but the real engineering win is the validation strategy.
On binary size, static linking with LTO should handle most of the bloat without needing custom stdlib builds.
We really need an AI filter here on HN.
A comment like this works as well, let the community do its thing.
There are a couple of bots here.
Quoting a user:
keeping it simple: a flat $15,000 to get you on the front page of Hacker News.
[...] contact e-mail below
Spend a week to do a bot, get 10'000 USD of ARR for your B2B tech SaaS, and applause from your investors.
And a week is probably exaggerated, 2 days max
Where I come from (Malawi, Africa), WhatsApp is so widespread that most people prefer it over email - to the extent that people don't really check their e-mails unless it's required for work or they are applying for something. For most people, WhatsApp is the de-facto communication channel.
I help moderate a community of developers and we hit the whatsapp group limit of 1024 members and sometimes have to wait for someone to leave (intentionally or accidentally) before we can add new members. We've tried to move people onto "better" platforms like Discord or Slack but we always end up coming back to WhatsApp which is subsidized via MNOs (mobile network operators) social media data/internet bundles and for the fact that most people are just stuck on whatsapp.
What one should do about this? I mean, beside working on lowering that number.
(Asking as a European who quite stubbornly refuses to install it - there are dozens of us. Dozens!)
Edit: please don't participate in making WhatsApp even more inescapable as it is today.
Force interoperability one way or another. WhatsApp is a closed system, if I want to use an alternative I'm stuck with adversarial interoperability, so stuff like Beeper (which is great, but...) which might get my account banned. Or waiting for some legislation to force WhatsApp to open it's API and let me interact with my contacts there without being locked into their apps
As a developer, I tried building an app that needs to use Whatsapp for communication. Unfortunately my phone number got blocked by the second test message. No Spam. Not marketing, just a test message to my own number. Along with it, they blocked my entire business, my LLC, and anything tied to it.
I have been trying to get hold of anyone or anything at Whatsapp. I've spent 6 months trying to navigate the bureaucracy. Facebook support claims they can't touch WhatsApp; WhatsApp support ignores the Facebook side. If you're building on WA, have a backup plan.
If any Whatsapp employee reading this can look into my WBA Account 1117362643780814
Telegram API is easier to handle as far as I know if that can somehow help (in case you want live ChatGPT or notifications for yourself in a mobile chat)
Telegram's bot API is a lot easier to get started with for sure. It's got some rough edges once you start trying to do anything more complex, though, and the underlying MTProto API is nothing short of bizarre.
I'd urge caution before using them as a component of your business, though. Their business strategy is pretty chaotic and has relied heavily on weird cryptocurrency-adjacent plays (e.g. TON / Fragment / gifts). They've made a couple of attempts to introduce business features, but I'm not sure they've had any substantial uptake.
Yeah telegram is so easy to develop with - I was blown away. I was able to spin up a bot that checks for GE appointments with minimal effort.
I will look into it. But my user base is either WhatsApp or plain SMS text messaging.
Advocate protocols over platforms. Have your government take an active interest in opening up closed communication systems and mandating third-party client access.
I guess if you want to lower that number, you'd need to build something better, in some way. Answered as another European who've had Whatsapp forever, as some stubborn people refuse to move away from it, and also bunch of businesses use it.
Network effect is killer. "better" would include having more than 3 billion people already on it.
Maybe the EU or China will crack down on it. A single company shouldn't decide who gets to talk to half the world. If that company is American they will not tolerate it for long.
Personally DeltaChat is my new favorite Thing but it falls afoul of Zooko's Triangle - A WhatsApp number or POTS number is short because it's centrally controlled and you have to pay for each one. DeltaChat has public keys, so I have 20 of them, and nobody can control who gets one, but they're incredibly long... the QR codes are nightmares.
WhatsApp happened at a time when, in Europe, you paid for SMS.
WhatsApp allowed people to send SMS without paying, or rather, paying just once to buy the app, so it was instantly valuable if you just convinced your spouse or parents or a single friend to install it.
To overcome it now, you need a lot more effort (or rely on enshittification, which I'm sure will happen).
Make your customer support on whatsapp. "Drop us a message to change your order". Allow ordering/enquiries over whatsapp.
Send 2 factor verification pins over whatsapp - it is more reliable than SMS and generally there is a better 1:1 mapping between whatsapp accounts and real humans than phone numbers, so it is a good anti-spam or good way to distribute "first month free" type deals whilst keeping abuse low.
Obviously make sure all URL's have info cards properly rendered in Whatsapp for good share-ability.
And now your customers are required to agree to Meta's term of services and to run some black box software, and you are screwed if Meta decides your business or your customers need to be kicked out.
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Can you describe your reasons? I haven't developed an opinion as no one here uses it.
I refuse to use proprietary software as much as I can, especially when it has a strong network effect where it encourages others to join.
Meta is also a despicable company, they don't need my help to succeed.
(edit: and I haven't abandoned the idea to switch back to a Linux mobile OS at some point, and WhatsApp would be a pain)
Sure, but like with most things, maybe like 200 million max of them in NA/EU would actually bring in real money.
Doesn't this description describe Facebook itself? Should we make apps more like that as well? Because they could not be more polar opposite each other.