resmon.exe

resmon.exe

Command: resmon.exe or resmon

Category: Diagnostics

Type: GUI

Purpose

Opens Windows Resource Monitor, providing real-time detailed monitoring of CPU, memory, disk, and network resource usage. More detailed than Task Manager but more accessible than Performance Monitor. Essential for identifying resource bottlenecks and understanding which processes are consuming system resources.

Quick Summary

Resource Monitor gives you a detailed, real-time view of exactly what's happening with your system resources. See which processes are using CPU, memory, disk, and network; drill down into file handles, network connections, and disk activity. Perfect for troubleshooting performance issues and identifying resource hogs without the complexity of Performance Monitor.

How to Use

1. Press Win + R to open the Run dialog.
2. Type resmon and press Enter.
3. Resource Monitor opens with five tabs: Overview, CPU, Memory, Disk, and Network.
4. Click any tab to see detailed information about that resource.
5. Use checkboxes next to processes to filter and highlight related activity.

Alternative methods:

• Type resmon in Command Prompt, PowerShell, or Start menu search
• Open Task Manager > Performance tab > "Open Resource Monitor" link at bottom
• Search for "Resource Monitor" in Start menu
• Run perfmon /res (same tool)

Main Tabs

Overview:

• Summary of all four resources in one view
• CPU, Memory, Disk, and Network graphs
• Key processes listed for each resource type

CPU:

• Processes and their CPU usage
• Associated handles (files, registry keys, etc.)
• Services running in each process
• CPU usage graph per core

Memory:

• Physical memory usage per process
• Commit charge and working set
• Memory composition (hardware reserved, in use, modified, standby, free)
• Memory usage graphs

Disk:

• Disk activity per process
• Files being accessed
• Read/write speeds per process
• Disk queue length and response time
• Storage details per physical disk

Network:

• Network activity per process
• Active TCP connections and listening ports
• Addresses being connected to
• Bytes sent/received per process
• Network adapter utilization

Tips and Best Practices

• Check a process to filter all views to show only that process's activity.
• Use the search box to quickly find specific processes.
• Right-click column headers to add or remove columns for more detail.
• Sort by any column to identify top consumers.
• Watch the graphs while performing problem activities to catch transient issues.
• Compare before and after starting applications to see their resource impact.
• Leave Resource Monitor open during troubleshooting to capture intermittent problems.

Common Use Cases

• High CPU usage: Identify which process is maxing out CPU and why.
• Memory leaks: Watch memory usage over time to spot processes consuming increasing memory.
• Disk bottlenecks: See which processes are causing high disk activity.
• Network issues: Identify processes consuming bandwidth or making unexpected connections.
• File access: See which processes have files open (helpful for "file in use" errors).
• Port conflicts: Identify which process is listening on or using specific ports.
• Performance slowdowns: Pinpoint resource bottlenecks in real-time.

Prerequisites

• No administrator rights required to view most information
• Administrator rights recommended for complete visibility
• Available on Windows Vista and later
• Uses minimal resources itself (~20-30 MB RAM)

CPU Tab Features

Processes Section:

• Image: Process name
• PID: Process ID
• Description: Application description
• Threads: Number of threads
• CPU: Current CPU usage
• Average CPU: Average over time

Associated Handles:

• Files, registry keys, and objects the selected process has open
• Useful for identifying what a process is doing

Associated Modules:

• DLLs and modules loaded by the selected process

Memory Tab Features

Processes Section:

• Commit (KB): Virtual memory committed
• Working Set (KB): Physical RAM currently used
• Shareable (KB): Memory that can be shared
• Private (KB): Memory exclusive to process

Physical Memory Graph:

• Hardware Reserved: Reserved by firmware
• In Use: Active memory
• Modified: Changed but not yet written to disk
• Standby: Cache that can be repurposed
• Free: Available for immediate use

Disk Tab Features

Processes with Disk Activity:

• Read and write speeds per process
• Total bytes read/written
• I/O priority

Disk Activity:

• Specific files being read or written
• File path and operation type

Storage:

• Physical disk information
• Active time, available space, queue length
• Disk performance graphs

Network Tab Features

Processes with Network Activity:

• Bytes sent/received per second
• Total bytes transferred

Network Activity:

• Specific addresses being contacted
• Sent and received byte counts per connection

TCP Connections:

• Local and remote addresses and ports
• Connection state
• Packet loss percentage

Listening Ports:

• Which processes are listening on which ports
• Firewall status for each port

Filtering and Analysis

Filter by process:

1. Check the box next to any process name
2. All sections filter to show only that process's activity
3. Related activity is highlighted across all tabs

Multiple process selection:

• Check multiple processes to compare their resource usage
• Highlight shows combined activity

Real-time graphs:

• 60-second rolling window
• Green line: Overall usage
• Other colors: Individual process usage (when checked)

Troubleshooting Specific Issues

"What's using all my CPU?"

1. Go to CPU tab
2. Sort by "CPU" column (descending)
3. Check top processes to filter their activity
4. Look at "Associated Handles" to see what they're accessing

"What's causing disk thrashing?"

1. Go to Disk tab
2. Sort by "Total (B/sec)" to find highest disk activity
3. Check "Disk Activity" section to see specific files
4. Identify if it's reading, writing, or both

"What's using my network bandwidth?"

1. Go to Network tab
2. Sort by "Total (B/sec)" to find network hogs
3. Check "Network Activity" to see destination addresses
4. Identify unexpected or suspicious connections

"Why can't I delete this file?"

1. Go to CPU tab
2. Search for filename in "Associated Handles"
3. Identifies which process has the file open
4. End process or close application to release file

Understanding the Graphs

CPU Graph:

• One graph per logical processor
• Shows current usage percentage
• Green = overall, other colors = selected processes

Memory Graph:

• Shows physical memory usage over time
• Includes hard faults per second (page faults requiring disk access)

Disk Graph:

• Shows disk I/O per second
• Queue length indicates disk congestion

Network Graph:

• Shows network throughput in Kbps or Mbps
• Separate graphs per network adapter

Troubleshooting

• High Resource Monitor CPU usage - Normal when monitoring; it needs resources to monitor resources.
• Some information not visible - Run as Administrator for complete access.
• Can't end process - Process may be protected; use Task Manager or command line with admin rights.
• Graphs not updating - Click "Pause" button to ensure it's not paused.
• Network section empty - May need to wait a few seconds for connections to populate.

Comparison with Other Tools

Task Manager:

• Simpler, less detailed
• Good for quick overview
• Easy access to end tasks

Resource Monitor (resmon):

• More detailed than Task Manager
• Real-time filtering and correlation
• Better for active troubleshooting

Performance Monitor (perfmon):

• Most detailed and configurable
• Can log data for historical analysis
• Steeper learning curve
• Better for long-term monitoring

Keyboard Shortcuts

• F1: Help
• F5: Refresh display
• Ctrl + F: Find/search
• Ctrl + Shift + Esc: Open Task Manager (if you need to switch)

Performance Impact

Resource Monitor itself uses:

• CPU: 1-3% typically
• Memory: 20-40 MB
• Minimal disk and network impact
• Safe to leave open during troubleshooting

Related Tools

• taskmgr.exe - Task Manager for basic monitoring
• perfmon.msc - Performance Monitor for advanced monitoring
• tasklist - Command-line process list
• netstat -ano - Network connections with PIDs
• Process Explorer (Sysinternals) - Even more detailed process information
• Process Monitor (Sysinternals) - Real-time file system, registry, and process monitoring