diff --git a/src/mdio/api/io.py b/src/mdio/api/io.py
index e72cafeb3..2e34e67ea 100644
--- a/src/mdio/api/io.py
+++ b/src/mdio/api/io.py
@@ -6,11 +6,14 @@
 from typing import Any
 from typing import Literal
 
+import zarr
 from upath import UPath
 from xarray import Dataset as xr_Dataset
 from xarray import open_zarr as xr_open_zarr
 from xarray.backends.api import to_zarr as xr_to_zarr
 
+from mdio.constants import ZarrFormat
+
 if TYPE_CHECKING:
     from collections.abc import Mapping
     from pathlib import Path
@@ -47,7 +50,13 @@ def open_mdio(input_path: UPath | Path | str, chunks: T_Chunks = None) -> xr_Dat
     """
     input_path = _normalize_path(input_path)
     storage_options = _normalize_storage_options(input_path)
-    return xr_open_zarr(input_path.as_posix(), chunks=chunks, storage_options=storage_options)
+    zarr_format = zarr.config.get("default_zarr_format")
+    return xr_open_zarr(
+        input_path.as_posix(),
+        chunks=chunks,
+        storage_options=storage_options,
+        mask_and_scale=zarr_format == ZarrFormat.V3,  # off for v2, on for v3
+    )
 
 
 def to_mdio(  # noqa: PLR0913
@@ -57,7 +66,6 @@ def to_mdio(  # noqa: PLR0913
     *,
     compute: bool = True,
     region: Mapping[str, slice | Literal["auto"]] | Literal["auto"] | None = None,
-    zarr_format: int = 3,
 ) -> None:
     """Write dataset contents to an MDIO output_path.
 
@@ -74,18 +82,17 @@ def to_mdio(  # noqa: PLR0913
             can be computed to write array data later. Metadata is always updated eagerly.
         region: Optional mapping from dimension names to either a) ``"auto"``, or b) integer slices, indicating
             the region of existing MDIO array(s) in which to write this dataset's data.
-        zarr_format: The desired zarr format to target. The default is 3.
     """
     output_path = _normalize_path(output_path)
     storage_options = _normalize_storage_options(output_path)
+    zarr_format = zarr.config.get("default_zarr_format")
     xr_to_zarr(
         dataset,
         store=output_path.as_posix(),  # xarray doesn't like URI when file:// is protocol
         mode=mode,
         compute=compute,
-        consolidated=False,
+        consolidated=zarr_format == ZarrFormat.V2,  # off for v3, on for v2
         region=region,
         storage_options=storage_options,
-        zarr_format=zarr_format,
         write_empty_chunks=False,
     )
diff --git a/src/mdio/constants.py b/src/mdio/constants.py
index 0036f5a90..783623281 100644
--- a/src/mdio/constants.py
+++ b/src/mdio/constants.py
@@ -1,9 +1,19 @@
 """Constant values used across MDIO."""
 
+from enum import IntEnum
+
 import numpy as np
 
 from mdio.schemas.dtype import ScalarType
 
+
+class ZarrFormat(IntEnum):
+    """Zarr version enum."""
+
+    V2 = 2
+    V3 = 3
+
+
 FLOAT16_MAX = np.finfo("float16").max
 FLOAT16_MIN = np.finfo("float16").min
 
diff --git a/src/mdio/core/grid.py b/src/mdio/core/grid.py
index 97e3bfac2..2a515334d 100644
--- a/src/mdio/core/grid.py
+++ b/src/mdio/core/grid.py
@@ -7,9 +7,11 @@
 
 import numpy as np
 import zarr
+from numcodecs.zarr3 import Blosc
 from zarr.codecs import BloscCodec
 
 from mdio.constants import UINT32_MAX
+from mdio.constants import ZarrFormat
 from mdio.core.utils_write import get_constrained_chunksize
 
 if TYPE_CHECKING:
@@ -108,8 +110,15 @@ def build_map(self, index_headers: HeaderArray) -> None:
             dtype=map_dtype,
             max_bytes=self._INTERNAL_CHUNK_SIZE_TARGET,
         )
-        grid_compressor = BloscCodec(cname="zstd")
-        common_kwargs = {"shape": live_shape, "chunks": chunks, "compressors": grid_compressor, "store": None}
+
+        zarr_format = zarr.config.get("default_zarr_format")
+
+        common_kwargs = {"shape": live_shape, "chunks": chunks, "store": None}
+        if zarr_format == ZarrFormat.V2:
+            common_kwargs["compressors"] = Blosc(cname="zstd")
+        else:
+            common_kwargs["compressors"] = BloscCodec(cname="zstd")
+
         self.map = zarr.create_array(fill_value=fill_value, dtype=map_dtype, **common_kwargs)
         self.live_mask = zarr.create_array(fill_value=0, dtype=bool, **common_kwargs)
 
diff --git a/src/mdio/core/utils_write.py b/src/mdio/core/utils_write.py
index 0414ecf6d..ab3c14f33 100644
--- a/src/mdio/core/utils_write.py
+++ b/src/mdio/core/utils_write.py
@@ -7,7 +7,6 @@
 
 if TYPE_CHECKING:
     from numpy.typing import DTypeLike
-    from zarr import Group
 
 
 MAX_SIZE_LIVE_MASK = 512 * 1024**2
@@ -15,17 +14,6 @@
 JsonSerializable = str | int | float | bool | None | dict[str, "JsonSerializable"] | list["JsonSerializable"]
 
 
-def write_attribute(name: str, attribute: JsonSerializable, zarr_group: "Group") -> None:
-    """Write a mappable to Zarr array or group attribute.
-
-    Args:
-        name: Name of the attribute.
-        attribute: Mapping to write. Must be JSON serializable.
-        zarr_group: Output group or array.
-    """
-    zarr_group.attrs[name] = attribute
-
-
 def get_constrained_chunksize(
     shape: tuple[int, ...],
     dtype: "DTypeLike",
@@ -45,7 +33,7 @@ def get_constrained_chunksize(
     return tuple(_balance_chunksizes(chunk)[0] for chunk in chunks)
 
 
-def get_live_mask_chunksize(shape: tuple[int, ...]) -> tuple[int]:
+def get_live_mask_chunksize(shape: tuple[int, ...]) -> tuple[int, ...]:
     """Given a live_mask shape, calculate the optimal write chunk size.
 
     Args:
diff --git a/src/mdio/schemas/v1/dataset_serializer.py b/src/mdio/schemas/v1/dataset_serializer.py
index 1e0a92d77..0df24a019 100644
--- a/src/mdio/schemas/v1/dataset_serializer.py
+++ b/src/mdio/schemas/v1/dataset_serializer.py
@@ -1,8 +1,10 @@
 """Convert MDIO v1 schema Dataset to Xarray DataSet and write it in Zarr."""
 
 import numpy as np
+import zarr
 from dask import array as dask_array
 from dask.array.core import normalize_chunks
+from numcodecs import Blosc
 from xarray import DataArray as xr_DataArray
 from xarray import Dataset as xr_Dataset
 from zarr.codecs import BloscCodec
@@ -16,6 +18,7 @@
 except ImportError:
     zfpy_ZFPY = None  # noqa: N816
 
+from mdio.constants import ZarrFormat
 from mdio.constants import fill_value_map
 from mdio.schemas.compressors import ZFP as mdio_ZFP  # noqa: N811
 from mdio.schemas.compressors import Blosc as mdio_Blosc
@@ -121,13 +124,17 @@ def _get_zarr_chunks(var: Variable, all_named_dims: dict[str, NamedDimension]) -
 
 def _convert_compressor(
     compressor: mdio_Blosc | mdio_ZFP | None,
-) -> BloscCodec | zfpy_ZFPY | None:
+) -> BloscCodec | Blosc | zfpy_ZFPY | None:
     """Convert a compressor to a numcodecs compatible format."""
     if compressor is None:
         return None
 
     if isinstance(compressor, mdio_Blosc):
-        return BloscCodec(**compressor.model_dump(exclude={"name"}))
+        blosc_kwargs = compressor.model_dump(exclude={"name"}, mode="json")
+        if zarr.config.get("default_zarr_format") == ZarrFormat.V2:
+            blosc_kwargs["shuffle"] = -1 if blosc_kwargs["shuffle"] is None else blosc_kwargs["shuffle"]
+            return Blosc(**blosc_kwargs)
+        return BloscCodec(**blosc_kwargs)
 
     if isinstance(compressor, mdio_ZFP):
         if zfpy_ZFPY is None:
@@ -215,12 +222,20 @@ def to_xarray_dataset(mdio_ds: Dataset) -> xr_Dataset:  # noqa: PLR0912
         if v.long_name:
             data_array.attrs["long_name"] = v.long_name
 
+        zarr_format = zarr.config.get("default_zarr_format")
+        fill_value_key = "_FillValue" if zarr_format == ZarrFormat.V2 else "fill_value"
+        fill_value = _get_fill_value(v.data_type) if v.name != "headers" else None
+
         encoding = {
             "chunks": original_chunks,
             "compressor": _convert_compressor(v.compressor),
-            "fill_value": _get_fill_value(v.data_type),
+            fill_value_key: fill_value,
         }
 
+        if zarr_format == ZarrFormat.V2:
+            encoding["chunk_key_encoding"] = {"name": "v2", "configuration": {"separator": "/"}}
+            print(encoding)
+
         data_array.encoding = encoding
 
         # Let's store the data array for the second pass
diff --git a/src/mdio/segy/blocked_io.py b/src/mdio/segy/blocked_io.py
index db066b260..fbd7531ae 100644
--- a/src/mdio/segy/blocked_io.py
+++ b/src/mdio/segy/blocked_io.py
@@ -10,6 +10,7 @@
 from typing import TYPE_CHECKING
 
 import numpy as np
+import zarr
 from dask.array import Array
 from dask.array import map_blocks
 from psutil import cpu_count
@@ -17,6 +18,7 @@
 from zarr import open_group as zarr_open_group
 
 from mdio.api.io import _normalize_storage_options
+from mdio.constants import ZarrFormat
 from mdio.core.indexing import ChunkIterator
 from mdio.schemas.v1.stats import CenteredBinHistogram
 from mdio.schemas.v1.stats import SummaryStatistics
@@ -118,6 +120,9 @@ def to_zarr(  # noqa: PLR0913, PLR0915
     attr_json = final_stats.model_dump_json()
     zarr_group[data_variable_name].attrs.update({"statsV1": attr_json})
 
+    if zarr.config.get("default_zarr_format") == ZarrFormat.V2:
+        zarr.consolidate_metadata(zarr_group.store)
+
     return final_stats