diff --git a/docs/releasenotes.md b/docs/releasenotes.md
index cf54708..43fe6b9 120000
--- a/docs/releasenotes.md
+++ b/docs/releasenotes.md
@@ -1 +1 @@
-../CHANGES.md
\ No newline at end of file
+../CHANGES.md
diff --git a/src/cooler/cli/cload.py b/src/cooler/cli/cload.py
index ded4b19..d1f52af 100644
--- a/src/cooler/cli/cload.py
+++ b/src/cooler/cli/cload.py
@@ -1,10 +1,14 @@
 import sys
 
 import click
+from .. import create_cooler
 import h5py
+import io
+import gzip
 import numpy as np
 import pandas as pd
 import simplejson as json
+from typing import Union
 from cytoolz import compose
 from multiprocess import Pool
 
@@ -24,10 +28,10 @@
     from pandas.io.common import get_handle
 
 
-# Copied from pairtools._headerops
 def get_header(instream, comment_char="#"):
-    """Returns a header from the stream and an the reaminder of the stream
+    """Returns a header from the stream and the remainder of the stream
     with the actual data.
+
     Parameters
     ----------
     instream : a file object
@@ -41,39 +45,94 @@ def get_header(instream, comment_char="#"):
         The header lines, stripped of terminal spaces and newline characters.
     remainder_stream : stream/file-like object
         Stream with the remaining lines.
-
     """
-    header = []
     if not comment_char:
         raise ValueError("Please, provide a comment char!")
-    comment_byte = comment_char.encode()
-    # get peekable buffer for the instream
-    read_f, peek_f = None, None
-    if hasattr(instream, "buffer"):
-        peek_f = instream.buffer.peek
-        readline_f = instream.buffer.readline
-    elif hasattr(instream, "peek"):
-        peek_f = instream.peek
-        readline_f = instream.readline
-    else:
-        raise ValueError("Cannot find the peek() function of the provided stream!")
 
-    current_peek = peek_f(1)
-    while current_peek.startswith(comment_byte):
-        # consuming a line from buffer guarantees
-        # that the remainder of the buffer starts
-        # with the beginning of the line.
+    header = []
+    buffered_lines = []
+    readline_f = instream.readline
+    is_bytes = False
+
+    while True:
         line = readline_f()
+        if not line:  # End of stream
+            break
         if isinstance(line, bytes):
+            is_bytes = True
             line = line.decode()
-        # append line to header, since it does start with header
+        if not line.startswith(comment_char):
+            buffered_lines.append(line)
+            break
         header.append(line.strip())
-        # peek into the remainder of the instream
-        current_peek = peek_f(1)
-    # apparently, next line does not start with the comment
-    # return header and the instream, advanced to the beginning of the data
-    return header, instream
 
+    # Create a new stream with the remaining data
+    from io import StringIO, BytesIO
+    if buffered_lines:
+        if is_bytes:
+            # For binary streams, read remaining data as bytes
+            remainder = instream.read()
+            if isinstance(remainder, str):
+                remainder = remainder.encode()
+            remainder_stream = BytesIO(b"".join([line.encode() for line in buffered_lines]) + remainder)
+        else:
+            # For text streams, read remaining data as text
+            remainder = instream.read()
+            if isinstance(remainder, bytes):
+                remainder = remainder.decode()
+            remainder_stream = StringIO("".join(buffered_lines) + remainder)
+    else:
+        remainder_stream = instream
+
+    return header, remainder_stream
+
+def open_maybe_gzip(path, mode="rt"):
+    if isinstance(path, str) and path.endswith(".gz"):
+        return gzip.open(path, mode)
+    return open(path, mode)
+
+def validate_pairs_columns(file_path: str, field_numbers: dict[str, int], is_stdin: bool = False) -> Union[io.StringIO, io.TextIOBase]:
+    """
+    Validate that column indices for chrom1, pos1, chrom2, pos2, and any additional fields
+    do not exceed the number of columns in the pairs file. Returns the stream positioned after headers.
+
+    Args:
+        file_path: Path to the pairs file or '-' for stdin.
+        field_numbers: Dictionary mapping field names (e.g., 'chrom1') to zero-based column indices.
+        is_stdin: True if input is from stdin.
+
+    Returns:
+        File-like object positioned at the start of data.
+
+    Raises:
+        ValueError: If any column index exceeds the number of columns in the file.
+    """
+    if is_stdin:
+        input_data = sys.stdin.read() if hasattr(sys.stdin, 'read') else sys.stdin.getvalue()
+        f = io.StringIO(input_data)
+    else:
+        f = open_maybe_gzip(file_path, 'r')
+
+    _, f = get_header(f, comment_char="#")
+    pos = f.tell()
+
+    # Read first data line and check column count
+    first_data_line = f.readline()
+    if isinstance(first_data_line, bytes):
+        first_data_line = first_data_line.decode()
+    first_data_line = first_data_line.strip()
+
+    f.seek(pos)  # Rewind to preserve the stream
+    if not first_data_line:
+        raise ValueError(f"Pairs file '{file_path}' is empty or contains only header lines")
+
+    num_cols = len(first_data_line.split("\t"))
+    for name, idx in field_numbers.items():
+        if idx >= num_cols:
+            raise ValueError(
+                f"Column index {idx + 1} ({name}) exceeds number of columns ({num_cols}) in '{file_path}'"
+            )
+    return f
 
 @cli.group()
 def cload():
@@ -551,9 +610,6 @@ def pairs(
     if len(field):
         for arg in field:
             name, colnum, dtype, agg = parse_field_param(arg)
-
-            # Special cases: these do not have input fields.
-            # Omit field number and agg to change standard dtypes.
             if colnum is None:
                 if (
                     agg is None
@@ -584,19 +640,12 @@ def pairs(
             else:
                 aggregations[name] = "sum"
 
-    # # Pairs counts are always produced, unless supressed explicitly
-    # do_count = not no_count
-    # if do_count:
-    #     if 'count' not in output_field_names:
-    #         output_field_names.append('count')  # default dtype and agg
-    # else:
-    #     if not len(output_field_names):
-    #         click.BadParameter(
-    #             "To pass `--no-count`, specify at least one input "
-    #             "value-column using `--field`.")
     if "count" not in output_field_names:
         output_field_names.append("count")
 
+    # Validate and get the stream
+    f_in = validate_pairs_columns(pairs_path, input_field_numbers, is_stdin=(pairs_path == "-"))
+
     # Customize the HDF5 filters
     if storage_options is not None:
         h5opts = parse_kv_list_param(storage_options)
@@ -606,19 +655,8 @@ def pairs(
     else:
         h5opts = None
 
-    # Initialize the input stream
-    # TODO: we could save the header into metadata
+    # Explicitly set kwargs to empty to avoid passing Click options to read_csv
     kwargs = {}
-    if pairs_path == "-":
-        f_in = sys.stdin
-    elif int(_pandas_version[0]) == 1 and int(_pandas_version[1]) < 2:
-        # get_handle returns a pair of objects in pandas 1.0 and 1.1
-        f_in = get_handle(pairs_path, mode="r", compression="infer")[0]
-    else:
-        # get_handle returns a single wrapper object in pandas 1.2+ and 2.*
-        f_in = get_handle(pairs_path, mode="r", compression="infer").handle
-
-    _, f_in = get_header(f_in)
 
     reader = pd.read_csv(
         f_in,
diff --git a/src/cooler/util.py b/src/cooler/util.py
index d25b65e..13e68eb 100644
--- a/src/cooler/util.py
+++ b/src/cooler/util.py
@@ -1,11 +1,12 @@
 from __future__ import annotations
 
+import io
 import os
 import re
 from collections import OrderedDict, defaultdict
 from collections.abc import Generator, Iterable, Iterator
 from contextlib import contextmanager
-from typing import IO, Any
+from typing import Any
 
 import h5py
 import numpy as np
@@ -204,16 +205,15 @@ def argnatsort(array: Iterable[str]) -> np.ndarray:
     cols = tuple(zip(*(natsort_key(x) for x in array)))
     return np.lexsort(cols[::-1])
 
-
 def read_chromsizes(
-    filepath_or: str | IO[str],
+    filepath_or: str | io.StringIO,
     name_patterns: tuple[str, ...] = (r"^chr[0-9]+$", r"^chr[XY]$", r"^chrM$"),
     all_names: bool = False,
     **kwargs,
 ) -> pd.Series:
     """
-    Parse a ``<db>.chrom.sizes`` or ``<db>.chromInfo.txt`` file from the UCSC
-    database, where ``db`` is a genome assembly name.
+    Parse a `<db>.chrom.sizes` or `<db>.chromInfo.txt` file from the UCSC
+    database, where `db` is a genome assembly name.
 
     Parameters
     ----------
@@ -221,32 +221,68 @@ def read_chromsizes(
         Path or url to text file, or buffer.
     name_patterns : sequence, optional
         Sequence of regular expressions to capture desired sequence names.
-        Each corresponding set of records will be sorted in natural order.
     all_names : bool, optional
-        Whether to return all contigs listed in the file. Default is
-        ``False``.
+        Whether to return all contigs listed in the file.
+    verbose : bool, optional
+        Whether to enable verbose logging for diagnostics.
+    """
+    # Handle URL case separately
+    if isinstance(filepath_or, str) and filepath_or.startswith(('http://', 'https://')):
+        try:
+            # Use pandas' built-in URL handling
+            chromtable = pd.read_csv(
+                filepath_or,
+                sep="\t",
+                usecols=[0, 1],
+                names=["name", "length"],
+                dtype={"name": str},
+                on_bad_lines="error",
+                **kwargs,
+            )
+        except Exception as e:
+            raise ValueError(f"Failed to fetch URL {filepath_or}: {e!s}") from e
+    else:
+        # Original validation for local files/StringIO
+        if isinstance(filepath_or, (str, io.StringIO)):
+            first_line = None
+            if isinstance(filepath_or, io.StringIO):
+                first_line = filepath_or.getvalue().splitlines()[0]
+            elif isinstance(filepath_or, str):
+                with open(filepath_or) as file:
+                    first_line = file.readline()
+
+            if first_line and ' ' in first_line:
+                raise ValueError(
+                    f"Chromsizes file '{filepath_or}' uses spaces instead of tabs "
+                    "as delimiters. Please use tabs.")
+
+        # Read the chromosome size file into a DataFrame
+        chromtable = pd.read_csv(
+            filepath_or,
+            sep="\t",  # Ensuring tab is the delimiter
+            usecols=[0, 1],
+            names=["name", "length"],
+            dtype={"name": str},
+            on_bad_lines="error",
+            **kwargs,
+        )
 
-    Returns
-    -------
-    :py:class:`pandas.Series`
-        Series of integer bp lengths indexed by sequence name.
+    # Convert the "length" column to numeric values, coercing errors to NaN
+    chromtable["length"] = pd.to_numeric(chromtable["length"], errors="coerce")
+
+    # Check for NaN values after conversion and raise an error if any are found.
+    if chromtable["length"].isnull().any():
+        raise ValueError(
+            f"Chromsizes file '{filepath_or}' contains missing or invalid length "
+            "values. "
+            "Please ensure that the file is properly formatted as tab-delimited with "
+            "two columns: "
+            "sequence name and integer length. "
+            "Check for extraneous spaces or hidden characters. "
+            f"Invalid rows: \n{chromtable[chromtable['length'].isnull()]}"
+        )
 
-    References
-    ----------
-    * `UCSC assembly terminology <http://genome.ucsc.edu/FAQ/FAQdownloads.html#download9>`_
-    * `GRC assembly terminology <https://www.ncbi.nlm.nih.gov/grc/help/definitions>`_
-
-    """
-    if isinstance(filepath_or, str) and filepath_or.endswith(".gz"):
-        kwargs.setdefault("compression", "gzip")
-    chromtable = pd.read_csv(
-        filepath_or,
-        sep="\t",
-        usecols=[0, 1],
-        names=["name", "length"],
-        dtype={"name": str},
-        **kwargs,
-    )
+    # Filter by patterns if needed
     if not all_names:
         parts = []
         for pattern in name_patterns:
@@ -254,6 +290,7 @@ def read_chromsizes(
             part = part.iloc[argnatsort(part["name"])]
             parts.append(part)
         chromtable = pd.concat(parts, axis=0)
+
     chromtable.index = chromtable["name"].values
     return chromtable["length"]
 
diff --git a/tests/test_cload.py b/tests/test_cload.py
new file mode 100644
index 0000000..d0f8cfd
--- /dev/null
+++ b/tests/test_cload.py
@@ -0,0 +1,210 @@
+from click.testing import CliRunner
+
+from cooler.cli.cload import pairs
+
+runner = CliRunner()
+
+
+def test_valid_indices(tmpdir):
+    """Test that valid column indices process successfully."""
+    bins_path = tmpdir.join("bins.bed")
+    pairs_path = tmpdir.join("pairs.txt")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\nchr1\t1000000\t2000000\nchr2\t0\t1000000\n")
+    pairs_path.write("chr1\t1000\tchr1\t2000\nchr1\t1500\tchr2\t3000\n")
+
+    result = runner.invoke(pairs, [
+        "-c1", "1",
+        "-p1", "2",
+        "-c2", "3",
+        "-p2", "4",
+        str(bins_path),
+        str(pairs_path),
+        str(out_path),
+    ])
+
+    assert result.exit_code == 0, f"Command failed: {result.output}"
+
+
+def test_invalid_index(tmpdir):
+    """Test that an invalid column index raises an error."""
+    bins_path = tmpdir.join("bins.bed")
+    pairs_path = tmpdir.join("pairs.txt")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\n")
+    pairs_path.write("chr1\t1000\tchr1\t2000\n")
+
+    result = runner.invoke(pairs, [
+        "-c1", "1",
+        "-p1", "2",
+        "-c2", "3",
+        "-p2", "5",
+        str(bins_path),
+        str(pairs_path),
+        str(out_path),
+    ])
+
+    assert result.exit_code != 0, "Command should have failed"
+    assert isinstance(result.exception, ValueError), (
+        f"Expected ValueError, got {result.exception}"
+    )
+    assert (
+        "Column index 5 (pos2) exceeds number of columns (4)" in str(result.exception)
+    ), (
+        f"Unexpected error: {result.exception}"
+    )
+
+
+def test_stdin_valid(tmpdir):
+    """Test valid indices with stdin input."""
+    bins_path = tmpdir.join("bins.bed")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\n")
+    pairs_data = "chr1\t1000\tchr1\t2000\n"
+
+    result = runner.invoke(
+        pairs,
+        [
+            "-c1", "1",
+            "-p1", "2",
+            "-c2", "3",
+            "-p2", "4",
+            str(bins_path),
+            "-",
+            str(out_path),
+        ],
+        input=pairs_data,
+    )
+
+    assert result.exit_code == 0, f"Command failed: {result.output} {result.exception}"
+
+
+def test_stdin_invalid(tmpdir):
+    """Test invalid index with stdin raises an error."""
+    bins_path = tmpdir.join("bins.bed")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\n")
+    pairs_data = "chr1\t1000\tchr1\t2000\n"
+
+    result = runner.invoke(
+        pairs,
+        [
+            "-c1", "1",
+            "-p1", "2",
+            "-c2", "3",
+            "-p2", "5",
+            str(bins_path),
+            "-",
+            str(out_path),
+        ],
+        input=pairs_data,
+    )
+
+    assert result.exit_code != 0, "Command should have failed"
+    assert isinstance(result.exception, ValueError), (
+        f"Expected ValueError, got {result.exception}"
+    )
+    assert (
+        "Column index 5 (pos2) exceeds number of columns (4)" in str(result.exception)
+    ), (
+        f"Unexpected error: {result.exception}"
+    )
+
+
+def test_header_skipping(tmpdir):
+    """Test that headers are skipped and validation works."""
+    bins_path = tmpdir.join("bins.bed")
+    pairs_path = tmpdir.join("pairs.txt")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\n")
+    pairs_path.write("#comment1\n#comment2\nchr1\t1000\tchr1\t2000\n")
+
+    result = runner.invoke(pairs, [
+        "-c1", "1",
+        "-p1", "2",
+        "-c2", "3",
+        "-p2", "4",
+        str(bins_path),
+        str(pairs_path),
+        str(out_path),
+    ])
+
+    assert result.exit_code == 0, f"Command failed: {result.output}"
+
+
+def test_empty_file(tmpdir):
+    """Test that an empty file or header-only file raises an error."""
+    bins_path = tmpdir.join("bins.bed")
+    pairs_path = tmpdir.join("pairs.txt")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\n")
+    pairs_path.write("#comment1\n#comment2\n")
+
+    result = runner.invoke(pairs, [
+        "-c1", "1",
+        "-p1", "2",
+        "-c2", "3",
+        "-p2", "4",
+        str(bins_path),
+        str(pairs_path),
+        str(out_path),
+    ])
+
+    assert result.exit_code != 0, "Command should have failed"
+    assert isinstance(result.exception, ValueError), (
+        f"Expected ValueError, got {result.exception}"
+    )
+    assert "is empty or contains only header lines" in str(result.exception), (
+        f"Unexpected error: {result.exception}"
+    )
+
+
+def test_extra_field(tmpdir):
+    """Test validation with an additional --field column."""
+    bins_path = tmpdir.join("bins.bed")
+    pairs_path = tmpdir.join("pairs.txt")
+    out_path = tmpdir.join("out.cool")
+
+    bins_path.write("chr1\t0\t1000000\nchr2\t0\t1000000\n")
+    pairs_path.write("chr1\t1000\tchr1\t2000\t1.5\nchr1\t1500\tchr2\t3000\t2.0\n")
+
+    result = runner.invoke(pairs, [
+        "-c1", "1",
+        "-p1", "2",
+        "-c2", "3",
+        "-p2", "4",
+        "--field", "value=5",
+        str(bins_path),
+        str(pairs_path),
+        str(out_path),
+    ])
+
+    assert result.exit_code == 0, f"Command failed: {result.output}"
+
+    # Test invalid extra field
+    result = runner.invoke(pairs, [
+        "-c1", "1",
+        "-p1", "2",
+        "-c2", "3",
+        "-p2", "4",
+        "--field", "value=6",
+        str(bins_path),
+        str(pairs_path),
+        str(out_path),
+    ])
+
+    assert result.exit_code != 0, "Command should have failed"
+    assert isinstance(result.exception, ValueError), (
+        f"Expected ValueError, got {result.exception}"
+    )
+    assert (
+        "Column index 6 (value) exceeds number of columns (5)" in str(result.exception)
+    ), (
+        f"Unexpected error: {result.exception}"
+    )
diff --git a/tests/test_util.py b/tests/test_util.py
index b3f94be..dcf1826 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -1,5 +1,5 @@
 import os.path as op
-from io import BytesIO
+from io import BytesIO, StringIO
 
 import h5py
 import numpy as np
@@ -166,6 +166,26 @@ def test_read_chromsizes():
     util.read_chromsizes(op.join(datadir, "toy.chrom.sizes"))
 
 
+def test_read_chromsizes_bad_input():
+    broken_data = "chr1\t1000\nchr2\tbad_value\nchr3\t2000\n"
+    broken_file = StringIO(broken_data)
+    with pytest.raises(ValueError):
+        util.read_chromsizes(broken_file)
+
+
+def test_read_chromsizes_bad_delimiter():
+    broken_data = "chr1 1000\nchr2 bad_value\nchr3 2000\n"
+    broken_file = StringIO(broken_data)
+    with pytest.raises(ValueError):
+        util.read_chromsizes(broken_file)
+
+
+# Main function to run the tests
+if __name__ == "__main__":
+    pytest.main([__file__])
+
+
+
 # def test_fetch_chromsizes():
 #     util.fetch_chromsizes("hg19")