Connector syntax

PQDriverless

Not part of the Power Query standard library. This function ships in PQDriverless, an open-source package of pure M readers for binary file formats — no ODBC driver, no OLE DB provider, nothing to install. Paste the M source into a blank query, or load PQDriverless.mez as a custom connector. See Installing.

Every driverless connector follows the same contract. Learn it once and the other thirteen behave the way you expect.

Reader.Function(
    source as binary,
    optional options as record
) as table

The source is always a binary

No connector takes a file path, a connection string or a URL. It takes bytes. That is the single design decision the whole thing rests on: acquiring the file and decoding the file are separate problems, and Power Query already solved the first one.

So the same call works wherever the file lives:

// local disk
Sqlite3.Database(File.Contents("C:\data\chinook.db"))

// SharePoint, OneDrive — refreshes in the Service with no gateway
Sqlite3.Database(SharePoint.Files("https://contoso.sharepoint.com/sites/data"){[Name = "chinook.db"]}[Content])

// Azure Blob storage
Sqlite3.Database(AzureStorage.Blobs("https://contoso.blob.core.windows.net/data"){[Name = "chinook.db"]}[Content])

// a public URL
Sqlite3.Database(Web.Contents("https://example.com/chinook.db"))

It also means a whole folder of files is a Table.AddColumn away:

let
    Files   = Folder.Files("C:\exports"),
    Dbfs    = Table.SelectRows(Files, each Text.Lower([Extension]) = ".dbf"),
    Decoded = Table.AddColumn(Dbfs, "Data", each Dbf.Table([Content]))
in
    Decoded

Credentials are whatever the source function already uses. The connectors never prompt for anything of their own.

Two output shapes

Single-table formats return the table directly. A .dbf file is one table, an .avro file is one stream of records, an .evtx file is one log:

Dbf.Table(File.Contents("C:\data\customers.dbf"))

Container formats return a navigation table. A database, a workbook or a .mat file holds several things, so the connector returns one row per item with the decoded value in a Data column. Drill in by name:

let
    db  = Sqlite3.Database(File.Contents("C:\data\chinook.db")),
    tbl = db{[Name = "tracks"]}[Data]
in
    tbl

The navigation table carries the ItemKind / ItemName / IsLeaf columns Power Query looks for, so in the editor you get the ordinary navigator experience — double-click a row instead of writing the lookup by hand.

Which connectors do what:

Shape	Connectors
Table	Dbf.Table, Avro.Document, Evtx.Document
Navigation table	Sqlite3.Database, Gpkg.Database, Mbtiles.Document, AccessReader.Database, Xls.Workbook, Xlsb.Workbook, Spss.Document, Stata.Document, Matlab.Document

Spss.Document and Stata.Document always return the same three rows — Data, Variables and ValueLabels — because a survey file's dictionary is worth as much as its cases.

The options record

The second argument is an optional record, and every key in it is optional too:

Dbf.Table(
    File.Contents("C:\data\customers.dbf"),
    [
        Memo     = File.Contents("C:\data\customers.fpt"),
        Encoding = 1252,
        MaxRows  = 1000
    ]
)

Four keys mean the same thing everywhere they appear:

Option	Type	Meaning
MaxRows	number	Stop after this many rows. Decoding actually stops — this is not a Table.FirstN over a full decode — so it is the right tool for probing a large unfamiliar file.
Strict	logical, default false	Turn tolerated malformations into errors. Off, a reader recovers what it can (a bad date becomes null, a corrupt EVTX chunk is skipped). On, it fails loudly. Use it to validate a file, not to load one.
Encoding	TextEncoding.Type or codepage number	Override the text encoding the file declares — or supply one for formats that declare nothing. Accepts a raw codepage number, which matters for the legacy formats where TextEncoding has no member for what you need.
PromoteHeaders	logical, default false	Use the first row as column headers. Workbook readers only.

They appear where they make sense, not on every connector: Matlab.Document takes only Encoding and Strict, because a .mat file is a set of variables rather than a row stream and there is nothing for MaxRows to stop.

Everything else is specific to the format, and is listed on that connector's page.

Metadata

Header facts that aren't rows — the file format version, the codepage, the creation date, how many records the header claimed — are attached to the result as metadata rather than smuggled into columns:

let
    t = Dbf.Table(File.Contents("C:\data\customers.dbf")),
    m = Value.Metadata(t)
in
    m[Dbf.Codepage]

Keys are namespaced by connector: Dbf.Version, Sqlite3.PageSize, Access.Version, Evtx.IsDirty, Spss.Product, Avro.Schema, and so on. Each connector page lists its own.

This is worth knowing about for one reason in particular: when a reader recovers from damage rather than failing, the metadata is where it tells you. A dirty event log reports Evtx.SkippedRecords, and a query that silently returns 40,000 of 41,000 events looks identical to one that returned everything unless you look.

Errors

Failures raise DataFormat.Error with a message that names the actual problem — an encrypted Access database, a Stata 7 file, a MAT-file saved as v7.3. The readers try hard not to fail obscurely: an unsupported format variant is detected and named rather than producing garbage rows.

Function naming

Names follow the convention Power Query already uses for its own readers, so that a connector reads like a built-in: .Database for a database file, .Workbook for a spreadsheet, .Table for a single-table file, and .Document for everything else.

One exception is worth knowing about. The Access reader is AccessReader.Database, not Access.Database, because that name is already a built-in engine function — a query can shadow it, but a section document cannot declare it, so the pasted reader and the packaged one would otherwise carry different names. One name, both delivery paths.