diff --git a/src/protein_quest/alphafold/confidence.py b/src/protein_quest/alphafold/confidence.py
index ffaa1b5..d4d8892 100644
--- a/src/protein_quest/alphafold/confidence.py
+++ b/src/protein_quest/alphafold/confidence.py
@@ -10,7 +10,7 @@
 from protein_quest.converter import Percentage, PositiveInt, converter
 from protein_quest.io import read_structure, write_structure
 from protein_quest.ss import nr_of_residues_in_total
-from protein_quest.utils import CopyMethod, copyfile
+from protein_quest.utils import Cacher, PassthroughCacher, copyfile
 
 """
 Methods to filter AlphaFoldDB structures on confidence scores.
@@ -113,7 +113,7 @@ class ConfidenceFilterResult:
 
 
 def filter_file_on_residues(
-    file: Path, query: ConfidenceFilterQuery, filtered_dir: Path, copy_method: CopyMethod = "copy"
+    file: Path, query: ConfidenceFilterQuery, filtered_dir: Path, cacher: Cacher | None = None
 ) -> ConfidenceFilterResult:
     """Filter a single AlphaFoldDB structure file (*.pdb[.gz], *.cif[.gz]) based on confidence.
 
@@ -121,12 +121,15 @@ def filter_file_on_residues(
         file: The path to the PDB file to filter.
         query: The confidence filter query.
         filtered_dir: The directory to save the filtered PDB file.
-        copy_method: How to copy when no residues have to be removed.
+        cacher: An optional cacher to use for caching downloaded files.
+            And copy method when no residues have to be removed.
 
     Returns:
         result with filtered_file property set to Path where filtered PDB file is saved.
             or None if structure was filtered out.
     """
+    if cacher is None:
+        cacher = PassthroughCacher()
     structure = read_structure(file)
     residues = set(find_high_confidence_residues(structure, query.confidence))
     count = len(residues)
@@ -138,16 +141,16 @@ def filter_file_on_residues(
             count=count,
         )
     total_residues = nr_of_residues_in_total(structure)
-    filtered_file = filtered_dir / file.name
+    filtered_file = filtered_dir / f"c{query.confidence}_{file.name}"
     if count == total_residues:
         # if no residues have to be removed then copy instead of slower gemmi writing
-        copyfile(file, filtered_file, copy_method)
+        copyfile(file, filtered_file, cacher.copy_method)
     else:
         new_structure = filter_out_low_confidence_residues(
             structure,
             residues,
         )
-        write_structure(new_structure, filtered_file)
+        write_structure(new_structure, filtered_file, cacher)
     return ConfidenceFilterResult(
         input_file=file.name,
         count=count,
@@ -159,7 +162,7 @@ def filter_files_on_confidence(
     alphafold_pdb_files: list[Path],
     query: ConfidenceFilterQuery,
     filtered_dir: Path,
-    copy_method: CopyMethod = "copy",
+    cacher: Cacher | None = None,
 ) -> Generator[ConfidenceFilterResult]:
     """Filter AlphaFoldDB structures based on confidence.
 
@@ -167,7 +170,8 @@ def filter_files_on_confidence(
         alphafold_pdb_files: List of mmcif/PDB files from AlphaFoldDB to filter.
         query: The confidence filter query containing the confidence thresholds.
         filtered_dir: Directory where the filtered mmcif/PDB files will be saved.
-        copy_method: How to copy when a direct copy is possible.
+        cacher: An optional cacher to use for caching downloaded files.
+            And copy method when no residues have to be removed.
 
     Yields:
         For each mmcif/PDB files yields whether it was filtered or not,
@@ -177,4 +181,4 @@ def filter_files_on_confidence(
     # In ../filter.py:filter_files_on_residues() we filter on number of residues on a file level
     # here we filter on file level and inside file remove low confidence residues
     for pdb_file in alphafold_pdb_files:
-        yield filter_file_on_residues(pdb_file, query, filtered_dir, copy_method)
+        yield filter_file_on_residues(pdb_file, query, filtered_dir, cacher)
diff --git a/src/protein_quest/cli.py b/src/protein_quest/cli.py
index a6ceefb..ad704cf 100644
--- a/src/protein_quest/cli.py
+++ b/src/protein_quest/cli.py
@@ -446,7 +446,7 @@ def _add_filter_confidence_parser(subparsers: argparse._SubParsersAction):
             In CSV format with `<input_file>,<residue_count>,<passed>,<output_file>` columns.
             Use `-` for stdout."""),
     )
-    _add_copy_method_arguments(parser)
+    _add_cacher_arguments(parser)
 
 
 def _add_filter_chain_parser(subparsers: argparse._SubParsersAction):
@@ -486,7 +486,7 @@ def _add_filter_chain_parser(subparsers: argparse._SubParsersAction):
             If not provided, will create a local cluster.
             If set to `sequential` will run tasks sequentially."""),
     )
-    _add_copy_method_arguments(parser)
+    _add_cacher_arguments(parser)
 
 
 def _add_filter_residue_parser(subparsers: argparse._SubParsersAction):
@@ -864,7 +864,7 @@ def _handle_filter_confidence(args: argparse.Namespace):
     min_residues = args.min_residues
     max_residues = args.max_residues
     stats_file: TextIOWrapper | None = args.write_stats
-    copy_method: CopyMethod = structure(args.copy_method, CopyMethod)  # pyright: ignore[reportArgumentType]
+    cacher = _initialize_cacher(args)
 
     output_dir.mkdir(parents=True, exist_ok=True)
     input_files = sorted(glob_structure_files(input_dir))
@@ -884,7 +884,7 @@ def _handle_filter_confidence(args: argparse.Namespace):
 
     passed_count = 0
     for r in tqdm(
-        filter_files_on_confidence(input_files, query, output_dir, copy_method=copy_method),
+        filter_files_on_confidence(input_files, query, output_dir, cacher=cacher),
         total=len(input_files),
         unit="file",
     ):
@@ -903,7 +903,7 @@ def _handle_filter_chain(args):
     output_dir = structure(args.output_dir, Path)
     pdb_id2chain_mapping_file = args.chains
     scheduler_address = structure(args.scheduler_address, str | None)  # pyright: ignore[reportArgumentType]
-    copy_method: CopyMethod = structure(args.copy_method, CopyMethod)  # pyright: ignore[reportArgumentType]
+    cacher = _initialize_cacher(args)
 
     # make sure files in input dir with entries in mapping file are the same
     # complain when files from mapping file are missing on disk
@@ -928,9 +928,7 @@ def _handle_filter_chain(args):
         rprint("[red]No valid structure files found. Exiting.")
         sys.exit(1)
 
-    results = filter_files_on_chain(
-        file2chain, output_dir, scheduler_address=scheduler_address, copy_method=copy_method
-    )
+    results = filter_files_on_chain(file2chain, output_dir, scheduler_address=scheduler_address, cacher=cacher)
 
     nr_written = len([r for r in results if r.passed])
 
diff --git a/src/protein_quest/filters.py b/src/protein_quest/filters.py
index 431f6f8..761cf37 100644
--- a/src/protein_quest/filters.py
+++ b/src/protein_quest/filters.py
@@ -12,7 +12,7 @@
 
 from protein_quest.parallel import configure_dask_scheduler, dask_map_with_progress
 from protein_quest.structure import nr_residues_in_chain, write_single_chain_structure_file
-from protein_quest.utils import CopyMethod, copyfile
+from protein_quest.utils import Cacher, CopyMethod, copyfile
 
 logger = logging.getLogger(__name__)
 
@@ -30,13 +30,13 @@ def filter_file_on_chain(
     file_and_chain: tuple[Path, str],
     output_dir: Path,
     out_chain: str = "A",
-    copy_method: CopyMethod = "copy",
+    cacher: Cacher | None = None,
 ) -> ChainFilterStatistics:
     input_file, chain_id = file_and_chain
     logger.debug("Filtering %s on chain %s", input_file, chain_id)
     try:
         output_file = write_single_chain_structure_file(
-            input_file, chain_id, output_dir, out_chain=out_chain, copy_method=copy_method
+            input_file, chain_id, output_dir, out_chain=out_chain, cacher=cacher
         )
         return ChainFilterStatistics(
             input_file=input_file,
@@ -53,7 +53,7 @@ def filter_files_on_chain(
     output_dir: Path,
     out_chain: str = "A",
     scheduler_address: str | Cluster | Literal["sequential"] | None = None,
-    copy_method: CopyMethod = "copy",
+    cacher: Cacher | None = None,
 ) -> list[ChainFilterStatistics]:
     """Filter mmcif/PDB files by chain.
 
@@ -65,7 +65,8 @@ def filter_files_on_chain(
         scheduler_address: The address of the Dask scheduler.
             If not provided, will create a local cluster.
             If set to `sequential` will run tasks sequentially.
-        copy_method: How to copy when a direct copy is possible.
+        cacher: An optional cacher to use for caching written files.
+            And copy method when file is copied without changes.
 
     Returns:
         Result of the filtering process.
@@ -74,7 +75,7 @@ def filter_files_on_chain(
     if scheduler_address == "sequential":
 
         def task(file_and_chain: tuple[Path, str]) -> ChainFilterStatistics:
-            return filter_file_on_chain(file_and_chain, output_dir, out_chain=out_chain, copy_method=copy_method)
+            return filter_file_on_chain(file_and_chain, output_dir, out_chain=out_chain, cacher=cacher)
 
         return list(map(task, file2chains))
 
@@ -93,7 +94,7 @@ def task(file_and_chain: tuple[Path, str]) -> ChainFilterStatistics:
             file2chains,
             output_dir=output_dir,
             out_chain=out_chain,
-            copy_method=copy_method,
+            cacher=cacher,
         )
 
 
diff --git a/src/protein_quest/io.py b/src/protein_quest/io.py
index 4367c01..d59bbda 100644
--- a/src/protein_quest/io.py
+++ b/src/protein_quest/io.py
@@ -1,5 +1,6 @@
 """Module for structure file input/output."""
 
+import asyncio
 import gzip
 import logging
 import shutil
@@ -17,7 +18,7 @@
 from mmcif.io.PdbxReader import PdbxReader
 from mmcif.io.PdbxWriter import PdbxWriter
 
-from protein_quest.utils import CopyMethod, copyfile, user_cache_root_dir
+from protein_quest.utils import Cacher, CopyMethod, PassthroughCacher, copyfile, user_cache_root_dir
 
 logger = logging.getLogger(__name__)
 
@@ -33,7 +34,7 @@
 """Set of valid structure file extensions."""
 
 
-def write_structure(structure: gemmi.Structure, path: Path):
+def write_structure(structure: gemmi.Structure, path: Path, cacher: Cacher | None = None):
     """Write a gemmi structure to a file.
 
     Args:
@@ -42,31 +43,37 @@ def write_structure(structure: gemmi.Structure, path: Path):
             The format depends on the file extension.
             See [StructureFileExtensions][protein_quest.io.StructureFileExtensions]
             for supported extensions.
+        cacher: An optional cacher to use for caching written files.
 
     Raises:
         ValueError: If the file extension is not supported.
     """
+    if cacher is None:
+        cacher = PassthroughCacher()
     if path.name.endswith(".pdb") or path.name.endswith(".ent"):
         body: str = structure.make_pdb_string()
-        path.write_text(body)
+        asyncio.run(cacher.write_bytes(path, body.encode("utf-8")))
     elif path.name.endswith(".pdb.gz") or path.name.endswith(".ent.gz"):
         body: str = structure.make_pdb_string()
-        with gzip.open(path, "wt") as f:
-            f.write(body)
+        gzbody: bytes = gzip.compress(body.encode("utf-8"))
+        asyncio.run(cacher.write_bytes(path, gzbody))
     elif path.name.endswith(".cif"):
         # do not write chem_comp so it is viewable by molstar
         # see https://github.com/project-gemmi/gemmi/discussions/362
         doc = structure.make_mmcif_document(gemmi.MmcifOutputGroups(True, chem_comp=False))
-        doc.write_file(str(path))
+        body = doc.as_string()
+        asyncio.run(cacher.write_bytes(path, body.encode("utf-8")))
     elif path.name.endswith(".cif.gz"):
         doc = structure.make_mmcif_document(gemmi.MmcifOutputGroups(True, chem_comp=False))
         cif_str = doc.as_string()
-        with gzip.open(path, "wt") as f:
-            f.write(cif_str)
+        gzbody: bytes = gzip.compress(cif_str.encode("utf-8"))
+        asyncio.run(cacher.write_bytes(path, gzbody))
     elif path.name.endswith(".bcif"):
         structure2bcif(structure, path)
+        # TODO write to cacher
     elif path.name.endswith(".bcif.gz"):
         structure2bcifgz(structure, path)
+        # TODO write to cacher
     else:
         msg = f"Unsupported file extension in {path.name}. Supported extensions are: {valid_structure_file_extensions}"
         raise ValueError(msg)
diff --git a/src/protein_quest/structure.py b/src/protein_quest/structure.py
index 31625a6..fe3c7eb 100644
--- a/src/protein_quest/structure.py
+++ b/src/protein_quest/structure.py
@@ -9,7 +9,7 @@
 
 from protein_quest.__version__ import __version__
 from protein_quest.io import read_structure, split_name_and_extension, write_structure
-from protein_quest.utils import CopyMethod, copyfile
+from protein_quest.utils import Cacher, PassthroughCacher, copyfile
 
 logger = logging.getLogger(__name__)
 
@@ -134,7 +134,7 @@ def write_single_chain_structure_file(
     chain2keep: str,
     output_dir: Path,
     out_chain: str = "A",
-    copy_method: CopyMethod = "copy",
+    cacher: Cacher | None = None,
 ) -> Path:
     """Write a single chain from a structure file to a new structure file.
 
@@ -157,7 +157,8 @@ def write_single_chain_structure_file(
         chain2keep: The chain to keep.
         output_dir: Directory to save the output file.
         out_chain: The chain identifier for the output file.
-        copy_method: How to copy when no changes are needed to output file.
+        cacher: An optional cacher to use for caching written files.
+            Also how to copy when no changes are needed to output file
 
     Returns:
         Path to the output structure file
@@ -166,6 +167,8 @@ def write_single_chain_structure_file(
         FileNotFoundError: If the input file does not exist.
         ChainNotFoundError: If the specified chain is not found in the input file.
     """
+    if cacher is None:
+        cacher = PassthroughCacher()
 
     logger.debug(f"chain2keep: {chain2keep}, out_chain: {out_chain}")
     structure = read_structure(input_file)
@@ -191,7 +194,7 @@ def write_single_chain_structure_file(
             out_chain,
             output_file,
         )
-        copyfile(input_file, output_file, copy_method)
+        copyfile(input_file, output_file, cacher.copy_method)
         return output_file
 
     gemmi.Selection(chain_name).remove_not_selected(structure)
@@ -203,6 +206,6 @@ def write_single_chain_structure_file(
     _dedup_sheets(structure, out_chain)
     _add_provenance_info(structure, chain_name, out_chain)
 
-    write_structure(structure, output_file)
+    write_structure(structure, output_file, cacher)
 
     return output_file
diff --git a/src/protein_quest/utils.py b/src/protein_quest/utils.py
index 1dcc884..de31933 100644
--- a/src/protein_quest/utils.py
+++ b/src/protein_quest/utils.py
@@ -57,6 +57,11 @@ def _cache_sub_dir(root_cache_dir: Path, filename: str, hash_length: int = 4) ->
 class Cacher(Protocol):
     """Protocol for a cacher."""
 
+    @property
+    def copy_method(self) -> CopyMethod:
+        """The copy method used by the cacher."""
+        ...
+
     def __contains__(self, item: str | Path) -> bool:
         """Check if a file is in the cache.
 
@@ -121,6 +126,11 @@ class PassthroughCacher(Cacher):
     On writes it just writes to the target path.
     """
 
+    @property
+    def copy_method(self) -> CopyMethod:
+        """The copy method used by the cacher."""
+        return "copy"
+
     def __contains__(self, item: str | Path) -> bool:
         # We don't have anything cached ever
         return False