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๐Ÿ“… Compatibility Dates

Compatibility Dates

Like the Workers runtime, Miniflare uses compatibility dates to opt-into backwards-incompatible changes from a specific date. If one isn't set, it will default to some time far in the past.

$ miniflare --compat-date 2021-11-12
compatibility_date = "2021-11-12"
const mf = new Miniflare({
compatibilityDate: "2021-11-12",

Compatibility Flags

Miniflare also lets you opt-in/out of specific changes using compatibility flags:

$ miniflare --compat-flag formdata_parser_supports_files --compat-flag durable_object_fetch_allows_relative_url
compatibility_flags = [
const mf = new Miniflare({
compatibilityFlags: [

Specifically Miniflare supports the following flags: