When we’re going to work with a file, it is usually a good idea to first test to ensure the file exists. The same is true in the world of web programming.

For instance, I have an article that demonstrates how you can download files from a URL:

and in it I trap the error that the file/resource cannot be accessed/located.  That said, it would be a good idea, to start off, by checking to ensure that the domain URL exists.

Furthermore, such functions can also be useful for validating data entry to ensure that someone didn’t make a typo.
 

The Solution

Option 1 – Microsoft WinHTTP Services

'---------------------------------------------------------------------------------------
' Procedure : WinHTTP_URLExist
' Author    : Daniel Pineault, CARDA Consultants Inc.
' Website   : http://www.cardaconsultants.com
' Purpose   : Check and see if a URL exists or not, based on the returned Status Code
' Copyright : The following is release as Attribution-ShareAlike 4.0 International
'             (CC BY-SA 4.0) - https://creativecommons.org/licenses/by-sa/4.0/
' Req'd Refs: Late Binding  -> None required
'             Early Binding -> Microsoft WinHTTP Services, version X.X
'
' Input Variables:
' ~~~~~~~~~~~~~~~~
' sURL      : URL to validate
'
' Usage:
' ~~~~~~
' ? WinHTTP_URLExist("https://www.google.ca")
'   Returns -> True
'
' Revision History:
' Rev       Date(yyyy-mm-dd)        Description
' **************************************************************************************
' 1         2012-07-07
' 2         2023-03-23              Updated Error Handling & Header
'---------------------------------------------------------------------------------------
Function WinHTTP_URLExist(ByVal sURL As String) As Boolean
    On Error GoTo Error_Handler
    #Const WinHTTP_EarlyBind = False   'True => Early Binding / False => Late Binding
    #If WinHTTP_EarlyBind = True Then
        Dim oWinHttp          As WinHttp.WinHttpRequest

        Set oWinHttp = New WinHttp.WinHttpRequest
    #Else
        Dim oWinHttp          As Object
        Const WinHttpRequestOption_UserAgentString = 0
        Const WinHttpRequestOption_EnableRedirects = 6

        Set oWinHttp = CreateObject("WinHttp.WinHttpRequest.5.1")
    #End If
    Dim lStatusCode           As Integer

    With oWinHttp
        .Option(WinHttpRequestOption_EnableRedirects) = False
        .Option(WinHttpRequestOption_UserAgentString) = "curl"
        .SetTimeouts 3000, 5000, 3000, 5000
        .Open "HEAD", sURL, False
        .Send
        lStatusCode = .Status
    End With
    WinHTTP_URLExist = (lStatusCode = 200)

Error_Handler_Exit:
    On Error Resume Next
    Set oWinHttp = Nothing
    Exit Function

Error_Handler:
    '-2147012889   The server name or address could not be resolved
    '-2147012894   The operation timed out
    If Err.Number <> -2147012889 And Err.Number <> -2147012894 Then
        MsgBox "The following error has occurred" & vbCrLf & vbCrLf & _
               "Error Source: WinHTTP_URLExist" & vbCrLf & _
               "Error Number: " & Err.Number & vbCrLf & _
               "Error Description: " & Err.Description & _
               Switch(Erl = 0, "", Erl <> 0, vbCrLf & "Line No: " & Erl) _
               , vbOKOnly + vbCritical, "An Error has Occurred!"
    End If
    Resume Error_Handler_Exit
End Function

Option 2 – Microsoft XML

'---------------------------------------------------------------------------------------
' Procedure : MSXML_URLExist
' Author    : Daniel Pineault, CARDA Consultants Inc.
' Website   : http://www.cardaconsultants.com
' Purpose   : Check and see if a URL exists or not, based on the returned Status Code
' Copyright : The following is release as Attribution-ShareAlike 4.0 International
'             (CC BY-SA 4.0) - https://creativecommons.org/licenses/by-sa/4.0/
' Req'd Refs: Late Binding  -> None required
'             Early Binding -> Microsoft XML, vX.X
'
' Input Variables:
' ~~~~~~~~~~~~~~~~
' sURL      : URL to validate
'
' Usage:
' ~~~~~~
' ? MSXML_URLExist("https://www.google.ca")
'   Returns -> True
' ? MSXML_URLExist("https://www.devhut.com")
'   Returns -> False
'
' Revision History:
' Rev       Date(yyyy-mm-dd)        Description
' **************************************************************************************
' 1         2012-07-07
' 2         2023-03-23              Updated Error Handling & Header
'---------------------------------------------------------------------------------------
Function MSXML_URLExist(ByVal sURL As String) As Boolean
'https://learn.microsoft.com/en-us/previous-versions/windows/desktop/ms760403(v=vs.85)
    On Error GoTo Error_Handler
    #Const MSXML_EarlyBind = False      'True => Early Binding / False => Late Binding
    #If MSXML_EarlyBind = True Then
        Dim oXMLHttp          As MSXML2.ServerXMLHTTP60

        Set oXMLHttp = New MSXML2.ServerXMLHTTP60
    #Else
        Dim oXMLHttp          As Object

        Set oXMLHttp = CreateObject("MSXML2.ServerXMLHTTP")
    #End If
    Dim lStatusCode           As Integer

    With oXMLHttp
        .SetTimeouts 3000, 5000, 3000, 5000
        .Open "HEAD", sURL, False
        .Send
        lStatusCode = .Status
    End With
    MSXML_URLExist = (lStatusCode = 200)

Error_Handler_Exit:
    On Error Resume Next
    Set oXMLHttp = Nothing
    Exit Function

Error_Handler:
    '-2147012889   The server name or address could not be resolved
    '-2147012894   The operation timed out
    If Err.Number <> -2147012889 And Err.Number <> -2147012894 Then
        MsgBox "The following error has occurred" & vbCrLf & vbCrLf & _
               "Error Source: MSXML_URLExist" & vbCrLf & _
               "Error Number: " & Err.Number & vbCrLf & _
               "Error Description: " & Err.Description & _
               Switch(Erl = 0, "", Erl <> 0, vbCrLf & "Line No: " & Erl) _
               , vbOKOnly + vbCritical, "An Error has Occurred!"
    End If
    Resume Error_Handler_Exit
End Function

HTTP Response Status Codes

Do note that in both instances I am validating the HTTP response status codes and only accepting a value of 200 as indicating that the URL is valid. This is a very strict definition of ‘valid’. So you may wish to review the complete list of HTTP response status codes using the link below and modify the validation to include other code, perhaps 200 – 299.

HTTP response status codes - HTTP | MDN

HTTP response status codes indicate whether a specific HTTP request has been successfully completed. Responses are grouped in five classes: