I've been periodically getting this error (invoking browser rendering via workers binding) ```Websoc

Wwelz I've been periodically getting this error (invoking browser rendering via worker...

K

Kathy•10/6/25, 8:16 PM

when did it start happening? and had you made any changes?

Wwelz Unable to create new browser: code: 503 Got this error a few times yesterday

W

welzOP•10/7/25, 5:25 PM

Getting this a bunch right now - is there a known issue?

Wwelz Getting this a bunch right now - is there a known issue?

P

Peps•10/7/25, 5:26 PM

there's a somewhat big incident going on right now, might be related: https://www.cloudflarestatus.com/incidents/ff4947s38tlb

Elevated workers KV timeouts

PPeps there's a somewhat big incident going on right now, might be related: https://ww...

K

Kathy•10/7/25, 5:39 PM

yes that's it. we're working on it rn

KKathy yes that's it. we're working on it rn

L

Lavinx•10/7/25, 5:48 PM

I keep getting “Workers are too busy” right now. Is that because of the current downtime in the Workers KV and effecting the REST API for PDF generation too?

LLavinx I keep getting “Workers are too busy” right now. Is that because of the current ...

K

Kathy•10/7/25, 6:16 PM

yes

KKathy yes

L

Lavinx•10/7/25, 6:17 PM

Thanks! Still receiving:

cURL error 28: Operation timed out after 30007 milliseconds with 0 bytes received (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://api.cloudflare.com/client/v4/accounts/XXXXX/browser-rendering/pdf

cURL error 28: Operation timed out after 30007 milliseconds with 0 bytes received (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://api.cloudflare.com/client/v4/accounts/XXXXX/browser-rendering/pdf

cURL error 28: Operation timed out after 30007 milliseconds with 0 bytes received (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://api.cloudflare.com/client/v4/accounts/XXXXX/browser-rendering/pdf

cURL error 28: Operation timed out after 30007 milliseconds with 0 bytes received (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://api.cloudflare.com/client/v4/accounts/XXXXX/browser-rendering/pdf

CloudFlare status mentions this issue has been resolved. Are the services being restored?

L

Lavinx•10/7/25, 6:25 PM

This seems to be resolved now. Back at

{"success":false,"errors":[{"message":"Browser is too busy","code":2000}]}

{"success":false,"errors":[{"message":"Browser is too busy","code":2000}]}

{"success":false,"errors":[{"message":"Browser is too busy","code":2000}]}

{"success":false,"errors":[{"message":"Browser is too busy","code":2000}]}

LLavinx This seems to be resolved now. Back at ``{"success":false,"errors":[{"message":"...

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Kathy•10/9/25, 6:00 PM

is this still happening? incident was resolved already

KKathy is this still happening? incident was resolved already

L

Lavinx•10/9/25, 7:13 PM

No, it has been resolved already. Thanks!

KKathy oh so timely. actually just finished PR for docs to add info on how you can add ...

C

Car1erX•10/10/25, 2:16 AM

your my hero

B

BlockMinister•10/10/25, 1:12 PM

hello, im constantly getting "The browser context is undefined. This means the CDP connection to the browser failed". this is for stagehand. using the following code as taken from the docs..

const stagehand = new Stagehand({
env: "LOCAL",
localBrowserLaunchOptions: { cdpUrl: endpointURLString(env.BROWSER) },
llmClient: new WorkersAIClient(env.AI),
verbose: 1,
});

await stagehand.init(); //errors here
const page = stagehand.page;

await page.goto('https://demo.playwright.dev/movies');

anyone get this working.

its being called from a CF workflow for context.

i have used the CF browser rendering successfully with pupetteer from the same project.

W

welzOP•10/12/25, 10:21 AM

Unable to create new browser: code: 503: message: No browser available

Unable to create new browser: code: 503: message: No browser available

Unable to create new browser: code: 503: message: No browser available

Unable to create new browser: code: 503: message: No browser available
getting this on my Workers

M

MisterWarung•10/12/25, 11:50 AM

Hi, hope that somebody can give me a hand: I want to develop a headless browser, where the user can browse like in a nowmal browser & can press a button to scrape the page that he sees? Is there something like that already out there that i might be capable to use or to build upon? Thx 4 the tipp

Wwelz `Unable to create new browser: code: 503: message: No browser available` getting...

K

kol3x•10/13/25, 8:54 AM

I also keep getting this, even though I have way less browser instances than "workers paid" allow

K

kol3x•10/13/25, 9:03 AM

On my browser rendering page I have "Average number of concurrent sessions - 0" and the history of browser sessions mostly have "Normal closure", but some sessions are missing "end time". Aren't they supposed to time out in 60s even if they weren't properly closed?

K

kol3x•10/13/25, 9:32 AM

I might be hitting this: "Rate limits are enforced with a fixed per-second fill rate. For example, a limit of 60 requests per minute translates to 1 request per second. This means you cannot send all 60 requests at once; the API expects them to be spread evenly over the minute. If your account has a custom higher limit, it will also be enforced as a per-second rate." source

Cloudflare Docs

Limits

Learn about the limits associated with Browser Rendering.

K

kol3x•10/14/25, 8:07 AM

No, that wasn't it. I even check my limits with puppeteer.limit(browser) first, and even though it says I have available browser - I get the same error anyway.

Wwelz `Unable to create new browser: code: 503: message: No browser available` getting...

K

Kathy•10/14/25, 5:33 PM

thanks for reporting. we made a change that should have resolved the 503s. can you confirm if working properly now?

cc: @kol3x as you had the same issue

Kkol3x On my browser rendering page I have "Average number of concurrent sessions - 0" ...

K

Kathy•10/14/25, 5:34 PM

this is odd - can you dm me with account id and session ids so we can look into this please?

BBlockMinister hello, im constantly getting "*The browser context is undefined. This means the ...

R

Rui Figueira•10/14/25, 5:40 PM

Hey @BlockMinister , are you running that code in the worker directly or is it in some Durable Object? Can you try the following code change?

      localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },

      localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },

      localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },

      localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },

(instead of passing

env.BROWSER

env.BROWSER

env.BROWSER

env.BROWSER binding object, pass the

"BROWSER"

"BROWSER"

"BROWSER"

"BROWSER" string to

endpointURLString

endpointURLString

endpointURLString

endpointURLString)

KKathy when using the rest api you can see the browser time used for every request in t...

S

SmallShen•10/14/25, 10:56 PM

How do I get

X-Browser-Ms-Used

X-Browser-Ms-Used

X-Browser-Ms-Used

X-Browser-Ms-Used value with typescript sdk? I think it is impossible with typescript sdk right now.

RRui Figueira Hey @BlockMinister , are you running that code in the worker directly or is it i...

B

BlockMinister•10/15/25, 2:35 PM

thanks for the reply, im using it in a Cloudflare Workflow step. I get a type script error when using the string as you suggested...

Argument of type 'string' is not assignable to parameter of type 'BrowserWorker'.ts

Argument of type 'string' is not assignable to parameter of type 'BrowserWorker'.ts

Argument of type 'string' is not assignable to parameter of type 'BrowserWorker'.ts

Argument of type 'string' is not assignable to parameter of type 'BrowserWorker'.ts

i deployed it anyway but it didnt work ,it failed with the same error as I reported previously.

BBlockMinister thanks for the reply, im using it in a Cloudflare Workflow step. I get a type...

R

Rui Figueira•10/15/25, 2:40 PM

that's strange, I have it running like this:

      const stagehand = new Stagehand({
        env: "LOCAL",
        localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },
        llmClient: new WorkersAIClient(env.AI, { logger }),
        logger,
        verbose: 1,
      });

      const stagehand = new Stagehand({
        env: "LOCAL",
        localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },
        llmClient: new WorkersAIClient(env.AI, { logger }),
        logger,
        verbose: 1,
      });

      const stagehand = new Stagehand({
        env: "LOCAL",
        localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },
        llmClient: new WorkersAIClient(env.AI, { logger }),
        logger,
        verbose: 1,
      });

      const stagehand = new Stagehand({
        env: "LOCAL",
        localBrowserLaunchOptions: { cdpUrl: endpointURLString("BROWSER") },
        llmClient: new WorkersAIClient(env.AI, { logger }),
        logger,
        verbose: 1,
      });

Can you check you're using

@cloudflare/playwright@1.0.0

@cloudflare/playwright@1.0.0

@cloudflare/playwright@1.0.0

@cloudflare/playwright@1.0.0 and that you have a browser binding named

BROWSER

BROWSER

BROWSER

BROWSER?

Mmarek Hey, any WebGL updates after two months, Kathy? 🙂

K

Kathy•10/16/25, 5:59 PM

hey WebGL should work now. Can yall confirm if working for your use cases?

@marek @katu @Jon M.

SSmallShen How do I get `X-Browser-Ms-Used` value with typescript sdk? I think it is imposs...

K

Kathy•10/17/25, 4:33 PM

Checked with the team -

I think it should work with .asResponse() method. Something like this:

const contentRes = await client.browserRendering.content.create({ account_id: 'account_id' }).asResponse();
const browserMsUsed = parseInt(contentRes.headers.get('X-Browser-Ms-Used') || '');

W

welzOP•10/21/25, 1:49 PM

Anyone else getting 503 errors when invoking from a worker binding?

G

gegi•10/22/25, 1:28 PM

Hello, can I cancel Browser Rendering calls with an abort signal?

Wwelz Anyone else getting 503 errors when invoking from a worker binding?

W

welzOP•10/22/25, 2:48 PM

and again...

Wwelz and again...

K

Kathy•10/22/25, 5:41 PM

you're right we had an incident yesterday and today. it's our top priority to get to the bottom of. major apologies

JJahvon I have another question related to the Stagehand integration - is there a way to...

E

Eric•10/22/25, 9:12 PM

@JDoc I've had this happen a ton locally, but it seems better in production. Did you experience that Playwright(-MCP), too? (I have)

A

ancs21•10/23/25, 10:21 AM

The issue concerns the parser start time.

Aancs21 The issue concerns the parser start time.

E

Eric•10/23/25, 9:45 PM

@Rui Figueira said in this issue that he'll report that to the team.

E

Eric•10/23/25, 9:51 PM

This may be more about #agents , but I'm surprised (or terrible at investigation) that https://github.com/cloudflare/playwright-mcp isn't

acquire

acquire

acquire

acquireing a dedicated browser for each agent session.

I would've expected it to internally do something like

routeAgentRequest

routeAgentRequest

routeAgentRequest

routeAgentRequest . I'm afraid that my agents are all referencing the same

env.BROWSER

env.BROWSER

env.BROWSER

env.BROWSER (but separate contexts)

N

NextMerge•10/27/25, 1:51 AM

Had a question regarding the Browser Rendering’s Rest API: In the docs it mentions that if a request is rate-limited, it’ll return a “Retry-After” header with the number of seconds until you can try again: https://developers.cloudflare.com/browser-rendering/platform/limits/#error-429-too-many-requests

From testing the api in curl it doesn’t seem to be including this header though. Even using the sample JS code shown ends up with a null retry count. When I was testing it last week I feel like it was including this header, so is this related to the outage that happened?

A

aem•10/30/25, 5:25 PM

Hiya, we're trying to port our PDF rendering from DocRaptor to the Browser Rendering API, but it seems like loading custom fonts via the REST API isn't working, and we'd like to avoid spinning up a worker just for this purpose. Is there a way to allow loading fonts via

style

style

style

style tags via the REST API that I'm not seeing or is that not an option? If not, is it on the roadmap?

Aaem Hiya, we're trying to port our PDF rendering from DocRaptor to the Browser Rende...

W

welzOP•10/31/25, 6:14 AM

I've loaded custom fonts from Google fonts - but invoking via Worker, might be different via API

Wwelz I've loaded custom fonts from Google fonts - but invoking via Worker, might be d...

A

aem•10/31/25, 2:46 PM

Yeah unfortunately we can't use Google fonts, we've got a custom font we self-host on our CDN. I know we can do this with a Worker, but we'd really rather not do that - our main app is hosted on GCP right now and building a GCP <> CF auth integration is more effort than it's worth to get fast PDF rendering

H

Hassan•11/1/25, 8:52 AM

Does anyone else have this issue?
curl -X 'POST' 'https://api.cloudflare.com/client/v4/accounts/9357fcd5fdd482d8ff83604451aad279/browser-rendering/markdown' \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer INkf8LWxNWrE96x4Z-zDCiAgoxMG6KfUuYvUAvyg' \
-d '{
"url": "https://www.czone.com.pk/graphic-cards-pakistan-ppt.154.aspx"
}'
{"success":true,"result":"# !Icon for www.czone.com.pkwww.czone.com.pk\n\nVerifying you are human. This may take a few seconds.
\n\nwww.czone.com.pk needs to review the security of your connection before proceeding.\n\nVerification successful\n\nWaiting for www.czone.com.pk to respond...\n\nRay ID:

997a23bf1a81339e

997a23bf1a81339e

997a23bf1a81339e

997a23bf1a81339e\n\nPerforman
ce & security by Cloudflare"}

I'm simply trying to get prices from a website and get blocked by cloudflare itself. So its not possible to use cloudflare browser rendering for website that use cloudflare?

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Celestial Rose•11/3/25, 10:45 AM

hey there ! using Stagehand in Browser Rendering I am wondering how to reuse sessions the same way its currently possible in Puppeteer as per these documentation : https://developers.cloudflare.com/browser-rendering/workers-bindings/reuse-sessions/
I am not sure I cant get to the browser sesh there and would love to not use DO for that

Cloudflare Docs

Reuse sessions

The best way to improve the performance of your browser rendering Worker is to reuse sessions. One way to do that is via Durable Objects, which allows you to keep a long running connection from a Worker to a browser. Another way is to keep the browser open after you've finished with it, and connect to that session each time you have a new request.

CCelestial Rose hey there ! using Stagehand in Browser Rendering I am wondering how to reuse ses...

C

Celestial Rose•11/3/25, 10:46 AM

maybe here ? https://docs.stagehand.dev/v3/best-practices/cost-optimization#3-optimize-browser-sessions

Stagehand Docs

Cost Optimization - 🤘 Stagehand

Minimize costs while maintaining automation performance

HHassan Does anyone else have this issue? curl -X 'POST' 'https://api.cloudflare.com/cli...

K

Kathy•11/4/25, 1:59 AM

Whether browser rendering can access a site or not depends on the settings of that site. So seems the site you are trying to use is blocking bots

Browser rendering always identifies itself as a bot, so if the site owner chooses to block all bots, then browser rendering will be blocked too.

if it's a site you own, you can create a rule to allow for browser rendering
https://developers.cloudflare.com/browser-rendering/faq/#will-browser-rendering-bypass-cloudflares-bot-protection

Cloudflare Docs

FAQ

Below you will find answers to our most commonly asked questions about Browser Rendering.

D

divby0•11/4/25, 8:22 AM

When trying to launch the browser inside a worker, it works 100% of the time. When launching from a workflow, it fails about half of the time with this error:

workerd/jsg/setup.c++:38: fatal: V8 fatal error; location = :0; message = Missing deoptimization information for OptimizedJSFrame::Summarize.

Aaem Yeah unfortunately we can't use Google fonts, we've got a custom font we self-ho...

K

Kathy•11/4/25, 11:44 PM

you can

addStyleTag

addStyleTag

addStyleTag

addStyleTag to customize. see example here https://developers.cloudflare.com/browser-rendering/rest-api/screenshot-endpoint/#customize-css-and-embed-custom-javascript

Cloudflare Docs

/screenshot - Capture screenshot

The /screenshot endpoint renders the webpage by processing its HTML and JavaScript, then captures a screenshot of the fully rendered page.

CCelestial Rose hey there ! using Stagehand in Browser Rendering I am wondering how to reuse ses...

K

Kathy•11/4/25, 11:46 PM

checked with the team:

They can use

keep_alive

keep_alive

keep_alive

keep_alive , eg

const browser = await puppeteer.launch(env.MYBROWSER, { keep_alive: 600000 });

const browser = await puppeteer.launch(env.MYBROWSER, { keep_alive: 600000 });

const browser = await puppeteer.launch(env.MYBROWSER, { keep_alive: 600000 });

const browser = await puppeteer.launch(env.MYBROWSER, { keep_alive: 600000 }); to keep the browser alive for 10 minutes, and then, in order to get a valid

sessionId

sessionId

sessionId

sessionId, they need to call

https://developers.cloudflare.com/browser-rendering/platform/puppeteer/#list-open-sessions

https://developers.cloudflare.com/browser-rendering/platform/puppeteer/#list-open-sessions

https://developers.cloudflare.com/browser-rendering/platform/puppeteer/#list-open-sessions

https://developers.cloudflare.com/browser-rendering/platform/puppeteer/#list-open-sessions .

Full example here https://developers.cloudflare.com/browser-rendering/workers-bindings/reuse-sessions/#4-code

Cloudflare Docs

Reuse sessions

The best way to improve the performance of your browser rendering Worker is to reuse sessions. One way to do that is via Durable Objects, which allows you to keep a long running connection from a Worker to a browser. Another way is to keep the browser open after you've finished with it, and connect to that session each time you have a new request.

KKathy checked with the team: They can use `keep_alive` , eg `const browser = await pu...

C

Celestial Rose•11/4/25, 11:48 PM

Hey! Thanks for your reply, I have found this link already, but does this work for stagehand ? This seems to only work for puppeteer; I literally posted this link in my OG post haha

I've been periodically getting this error (invoking browser rendering via workers binding) ```Websoc

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