Firebase emulator cloud function throws cors error when hit from frontend

Question

I have this function that works perfectly in production however when running locally I get cors errors

export const listUsers = functions.https.onRequest(async (req, res) => {
    res.set("Access-Control-Allow-Origin", "*")
    const data = await getSomeUsers(10)
    res.json(data)
})

emulators starts fine:

cors issue:

Please don't show images of text. Edit the question and copy the text into the question itself so it's easier to read, copy, and search. — Doug Stevenson
– Doug Stevenson, Commented Jun 17, 2020 at 21:53
I've been doing that for years, seems to me that the most important searchable stuff is already in there.. — Nikos
– Nikos, Commented Jun 19, 2020 at 17:55
I'm asking as a favor for all the people with disabilities that find small graphical text to be difficult or impossible to read. Also, please read this: meta.stackoverflow.com/questions/303812/… — Doug Stevenson
– Doug Stevenson, Commented Jun 19, 2020 at 19:31
They click on the image and it gets larger plus you have the colours. — Nikos
– Nikos, Commented Jun 20, 2020 at 18:13
That's not the way disabilities work. It's most helpful to simply copy the text into the question. — Doug Stevenson
– Doug Stevenson, Commented Jun 20, 2020 at 18:17

Ville Rinne · Accepted Answer · 2020-06-17 22:31:47Z

2

Check this:

Deadly CORS when http://localhost is the origin

Chrome does not support localhost for CORS requests (a bug opened in 2010, marked WontFix in 2014).

To get around this you can use a domain like lvh.me (which points at 127.0.0.1 just like localhost) or start chrome with the --disable-web-security flag (assuming you're just testing).

edited Jun 17, 2020 at 22:31

answered Jun 17, 2020 at 22:26

Ville Rinne

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5 Comments

Nikos Over a year ago

Can you tell me more about lvh.me ?

Bruno Over a year ago

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. - From Review

Ville Rinne Over a year ago

@bruno, isn't the essential part included in the quote?

Nikos Over a year ago

--disable-web-security works great thx for my issue

FuzzyLogic12 Over a year ago

Chrome does support CORS from localhost, this is extremely misleading. The bug was closed because it was not reproducible.

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