Console.log's not working in Production on Vercel

[taylorhlabs]

I am trying to debug a backend function in my app that is working fine in my lab but doesn't seem to be working in production. In my Vercel Dashboard, I'm not getting any errors or console.log's in my Functions log. According to this recent blog post, console.log's should show in the Functions log in the Vercel Dashboard. Am I missing some major import or dependency in production that would cause the function to fail spectacularly? I have Node installed globally on my local machine but I don't need to have Node as a dependency in my project for Vercel, do I?

My function is below. It fetches an image based on a URL and then tries to upload the image to a Google Cloud Storage bucket. As you can see, I have lots of logging, but none of them show in the Vercel Dashboard.

import axios from 'axios';
import { v4 as uuidv4 } from 'uuid';
import { Storage } from '@google-cloud/storage';

export default async function handle(req, res) {
  let { featuredImage } = req.body;

  console.log(featuredImage);

  // generate file name
  const imageName = uuidv4();
  console.log(imageName);

  // download featured image
  let downloaded;
  try {
    downloaded = await axios.get(featuredImage, {
      responseType: 'stream'
    });
  } catch (error) {
    console.log(`Error getting image url: ${error}`);
    // return original featuredImage url if unable to fetch the image directly
    res.json(featuredImage);
    return;
  }

  // check headers for image type
  const fileType = downloaded.headers['content-type'];
  console.log(fileType);
  if (!fileType) {
    console.log('No file type');
    // return empty image since it's likely invalid image format
    res.json('');
    return;
  }
  let imageExt = fileType.split('/')[1];
  console.log(imageExt);
  if (!imageExt) {
    console.log('No file extension');
    // return empty image since it's likely invalid image format
    res.json('');
    return;
  }

  // check if valid image type
  const supportedImageTypes = [ 'apng', 'avif', 'gif', 'jpg', 'jpeg', 'jfif', 'pjpeg', 'pjp', 'png', 'svg', 'webp' ];
  if (!supportedImageTypes.includes(imageExt)) {
    console.log('Not valid file type');
    // return empty image since it's likely invalid image format
    res.json('');
    return;
  }

  // if we made it this far, it's a valid image type
  console.log('Valid file type');

  // get ready to upload stream to GCP Storage
  const storage = new Storage({
    projectId: process.env.PROJECT_ID,
    credentials: {
      client_email: process.env.CLIENT_EMAIL,
      private_key: process.env.PRIVATE_KEY
    }
  });
  const myBucket = storage.bucket(process.env.BUCKET_NAME);
  const file = myBucket.file(`${imageName}.${imageExt}`);

  // upload to GCP Storage
  const uploaded = () => {
    return new Promise((resolve, reject) => {
      downloaded.data.pipe(file.createWriteStream({ gzip: true })).on('finish', resolve).on('error', reject);
    });
  };

  try {
    await uploaded();
  } catch (error) {
    console.log(`Error uploading image to GCP Storage: ${error}`);
    // server error of some kind.
    // if we made it this far, the featuredImage url is probably ok so return that
    res.json(featuredImage);
    return;
  }

  // set new url for image to match new image in GCP Storage
  featuredImage = `https://storage.googleapis.com/my-bucket-365c82f/${imageName}.${imageExt}`;
  res.json(featuredImage);
}

[taylorhlabs]

Console logging just started working like 15 minutes later. Is there a delay sometimes?

[roofleDev]

I've also had issues where the logs don't show up for an uncertain amount of time. I wish there was some insight into this behavior.

[redochka]

Same here, not clear what's happening. Sometimes when there is an uncaught error, vercel seems to swallow all logs... few hours later, logs seems to be there again... not reliable!

[BongBongBang]

same situation....

[jgreens]

@huozhi would it be possible to take a look? Thank you 🙏

[g-wozniak]

Same for me, no console.error(), no console.info() or console.log(); winston does not log anything either in Vercel. Sadly, this causes major issues due to inconsistency between local and Vercel environments with Postmark and serverless functions that suddenly stop execution.

[redochka]

The bug is here again. Had to deploy and make sure the "use cache" is unchecked and now it's working.

[joelbqz]

This bug is still present

[nvegater]

please check this.

[The-Poe]

Encounter the same issue again

[ThomasGHenry]

😭😭😭😭😭😭

[bask-digital]

Experiencing this with Nuxt

[iploooox]

still here.

[Yan-Doshchinskiy]

still here

[yashb042]

Still observed

[wangf1]

I encounter same issue. Console.log log did not appears in vercel dashboard logs tab.

[ralph-interworldhighway]

Still here....

[legitapps-25]

Still here

[KranzAklilu]

Damn. Logging is a critical feature on any cloud infrastructure you know :)

[maribox]

Found two possible solutions to this:

#59208 (comment)
#68332 (comment)

[FridayCandour]

still here in april 18 2025.

[rovshanr1]

still here in may 8 2025

[TradersEdge]

12.5.2025 still here

[samconsidine]

still here

[cga-ma]

WTH ? Still here

[rafadontal]

still here

[kwam12]

still here

[aryanbaburajan]

huh. still here?

[hireshBrem]

stll here, fr?

[apostolisCodpal]

This is quite crippling. I can see logs of api route return statuses, but not console.logs that I insert in my code. And this is an api endpoint so I don't see the reason.

[Will-Copeland]

Adding my name to the list. Function is failing in production only, fill it with logs, lo and behold nothing to see. 👍

Whats the point of logging if it doesnt work when something breaks? l o l

[Elvis557]

Thanks for the insights, this really helped!