diff --git a/CSVLintNppPlugin/CsvLint/CsvAnalyze.cs b/CSVLintNppPlugin/CsvLint/CsvAnalyze.cs
index ea1a770..04f9cb6 100644
--- a/CSVLintNppPlugin/CsvLint/CsvAnalyze.cs
+++ b/CSVLintNppPlugin/CsvLint/CsvAnalyze.cs
@@ -23,11 +23,16 @@ class CsvAnalyze
         /// <param name="autodetect">automatically detect separator and header names</param>
         /// <param name="mansep">Override automatic detection, manually provided column separator</param>
         /// <param name="manhead">Override automatic detection, manually set first header row contains columns names</param>
+        /// <param name="userRequested">if the inference was explicitly requested by the user (rather than auto-triggered on opening a file)</param>
         /// <returns></returns>
-        public static CsvDefinition InferFromData(bool autodetect, char mansep, string manwid, bool manhead, int manskip, char commchar)
+        public static CsvDefinition InferFromData(bool autodetect, char mansep, string manwid, bool manhead, int manskip, char commchar, bool userRequested)
         {
             // First do a letter frequency analysis on each row
-            var strfreq = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strfreq, userRequested))
+            {
+                var csvdef = new CsvDefinition { FileIsTooBig = true };
+                return csvdef;
+            }
             string line;
             int lineCount = 0, linesQuoted = 0, lineContent = 0;
 
@@ -326,7 +331,7 @@ public static CsvDefinition InferFromData(bool autodetect, char mansep, string m
             // reset string reader to first line is not possible, create a new one
             bool fixedwidth = result.Separator == '\0';
 
-            var strdata = ScintillaStreams.StreamAllText();
+            ScintillaStreams.TryStreamAllText(out var strdata);
 
             // examine data and keep statistics for each column
             List<CsvAnalyzeColumn> colstats = new List<CsvAnalyzeColumn>();
@@ -503,7 +508,8 @@ public static void StatisticalReportData(CsvDefinition csvdef)
             int lineCount = 0;
             bool fixedwidth = csvdef.Separator == '\0';
 
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out var strdata))
+                return;
 
             // skip any comment lines
             int commentCount = csvdef.SkipCommentLinesAtStart(strdata);
@@ -672,7 +678,8 @@ public static void CountUniqueValues(CsvDefinition csvdef, List<int> colidx, boo
         {
             // examine data and keep list of counters per unique values
             Dictionary<string, int> uniquecount = new Dictionary<string, int>();
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out var strdata))
+                return;
             List<string> values;
 
             bool iscomm = false;
diff --git a/CSVLintNppPlugin/CsvLint/CsvDefinition.cs b/CSVLintNppPlugin/CsvLint/CsvDefinition.cs
index 85b0593..91a79de 100644
--- a/CSVLintNppPlugin/CsvLint/CsvDefinition.cs
+++ b/CSVLintNppPlugin/CsvLint/CsvDefinition.cs
@@ -181,6 +181,9 @@ public void AddCodedValues(Dictionary<string, int> slcodes)
     /// </summary>
     public class CsvDefinition
     {
+        /// <summary>True if and only if the current file has more than <see cref="int.MaxValue"/> bytes</summary>
+        public bool FileIsTooBig { get; set; } = false;
+
         public int DefaultLanguageId { get; set; } = 0;
 
         /// column separator character
diff --git a/CSVLintNppPlugin/CsvLint/CsvEdit.cs b/CSVLintNppPlugin/CsvLint/CsvEdit.cs
index 215c391..d8e43a4 100644
--- a/CSVLintNppPlugin/CsvLint/CsvEdit.cs
+++ b/CSVLintNppPlugin/CsvLint/CsvEdit.cs
@@ -142,7 +142,8 @@ public static void ReformatDataFile(CsvDefinition csvdef, string reformatSeparat
             var CRLF = getEditorEOLchars(scintillaGateway.GetEOLMode());
 
             // use stringreader to go line by line
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strdata))
+                return;
 
             //var s = new StringReader(data);
             int linenr = 0;
@@ -481,7 +482,8 @@ public static void ConvertToSQL(CsvDefinition csvdef)
             if (enumcols1 != "") sb.Append(string.Format("-- Enumeration columns (optional)\r\n/*\r\n{0}{1}*/\r\n", enumcols1, enumcols2));
 
             // use stringreader to go line by line
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strdata))
+                return;
 
             int lineCount = csvdef.ColNameHeader ? -1 : 0;
             int batchcomm = -1;  // batch comment line
@@ -703,7 +705,8 @@ public static void ConvertToXML(CsvDefinition csvdef)
             sb.Append("\t-->\r\n");
 
             // use stringreader to go line by line
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strdata))
+                return;
 
             int lineCount = (csvdef.ColNameHeader ? -1 : 0);
 
@@ -847,7 +850,8 @@ public static void ConvertToJSON(CsvDefinition csvdef)
             sb.Append("\t\"JSONdata\":[");
 
             // use stringreader to go line by line
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strdata))
+                return;
 
             int lineCount = (csvdef.ColNameHeader ? -1 : 0);
 
@@ -1074,7 +1078,8 @@ public static void SortData(CsvDefinition csvdef, int SortIdx, bool AscDesc, boo
             // examine data and keep list of all data lines
             // Note: can be a dictionary, not a list, because the sortable values are guaranteed to be unique
             Dictionary<string, string> sortlines = new Dictionary<string, string>();
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strdata))
+                return;
 
             // variables to read original data file
             List<string> values;
@@ -1161,7 +1166,8 @@ public static void ColumnSplit(CsvDefinition csvdef, int ColumnIndex, int SplitC
             var CRLF = getEditorEOLchars(scintillaGateway.GetEOLMode());
 
             // use stringreader to go line by line
-            var strdata = ScintillaStreams.StreamAllText();
+            if (!ScintillaStreams.TryStreamAllText(out StreamReader strdata))
+                return;
 
             //var s = new StringReader(data);
             int linenr = 0;
diff --git a/CSVLintNppPlugin/Forms/CsvLintWindow.cs b/CSVLintNppPlugin/Forms/CsvLintWindow.cs
index 3771462..39f0ede 100644
--- a/CSVLintNppPlugin/Forms/CsvLintWindow.cs
+++ b/CSVLintNppPlugin/Forms/CsvLintWindow.cs
@@ -21,7 +21,13 @@ public void SetCsvDefinition(CsvDefinition csvdef, bool applybtn)
         {
             // clear message to user when no columns found
             var msg = "";
-            if ((csvdef.Fields.Count == 1) && (csvdef.Fields[0].DataType == ColumnType.String) && (csvdef.Fields[0].MaxWidth >= 9999))
+            if (csvdef.FileIsTooBig)
+            {
+                msg += "; *********************************\r\n";
+                msg += "; File is too large for CsvLint to analyze\r\n";
+                msg += "; *********************************\r\n";
+            }
+            else if ((csvdef.Fields.Count == 1) && (csvdef.Fields[0].DataType == ColumnType.String) && (csvdef.Fields[0].MaxWidth >= 9999))
             {
                 // give a clear message
                 msg += "; *********************************\r\n";
@@ -75,7 +81,7 @@ private void OnBtnDetectColumns_Click(object sender, EventArgs e)
                 var dtStart = DateTime.Now;
 
                 // analyze and determine csv definition
-                CsvDefinition csvdef = CsvAnalyze.InferFromData(chkAutoDetect.Checked, sep, widths, header, skip, comm);
+                CsvDefinition csvdef = CsvAnalyze.InferFromData(chkAutoDetect.Checked, sep, widths, header, skip, comm, true);
 
                 Main.UpdateCSVChanges(csvdef, false);
 
@@ -106,7 +112,8 @@ private void OnBtnValidate_Click(object sender, EventArgs e)
                 // validate data
                 CsvValidate csvval = new CsvValidate();
 
-                var sr = ScintillaStreams.StreamAllText();
+                if (!ScintillaStreams.TryStreamAllText(out var sr))
+                    return;
 
                 csvval.ValidateData(sr, csvdef);
 
diff --git a/CSVLintNppPlugin/Forms/DetectColumnsForm.cs b/CSVLintNppPlugin/Forms/DetectColumnsForm.cs
index 05d360d..d947f66 100644
--- a/CSVLintNppPlugin/Forms/DetectColumnsForm.cs
+++ b/CSVLintNppPlugin/Forms/DetectColumnsForm.cs
@@ -151,7 +151,8 @@ private void btnFixedWidthPos_Click(object sender, EventArgs e)
             if (dialogResult == DialogResult.OK)
             {
                 // paste column positions
-                CsvDefinition csvdef = Main.GetCurrentCsvDef();
+                if (!Main.TryGetCurrentCsvDef(out CsvDefinition csvdef))
+                    return;
                 txtFixedWidthPos.Text = csvdef.GetColumnWidths(true);
             }
         }
diff --git a/CSVLintNppPlugin/Main.cs b/CSVLintNppPlugin/Main.cs
index 08e974a..4e4bcdd 100644
--- a/CSVLintNppPlugin/Main.cs
+++ b/CSVLintNppPlugin/Main.cs
@@ -10,6 +10,7 @@
 using System.Windows.Forms;
 using System.Xml;
 using CSVLint;
+using CSVLint.Tools;
 using CSVLintNppPlugin.CsvLint;
 using CSVLintNppPlugin.Forms;
 using Kbg.NppPluginNET.PluginInfrastructure;
@@ -440,7 +441,7 @@ public static void CSVChangeFileTab()
                 else
                 {
                     // analyze and determine csv definition
-                    csvdef = CsvAnalyze.InferFromData(true, '\0', "", false, 0, Main.Settings.CommentCharacter); // parameters "", false, 0 -> defaults
+                    csvdef = CsvAnalyze.InferFromData(true, '\0', "", false, 0, Main.Settings.CommentCharacter, false); // parameters "", false, 0 -> defaults
                 }
                 FileCsvDef.Add(filename, csvdef);
             }
@@ -481,7 +482,8 @@ public static void CSVChangeFileTab()
         public static void EnableDisableLanguage()
         {
             Win32.SendMessage(PluginBase.nppData._nppHandle, (uint)NppMsg.NPPM_GETCURRENTLANGTYPE, 0, out int currentLanguageId);
-            CsvDefinition csvdef = GetCurrentCsvDef();
+            if (!TryGetCurrentCsvDef(out CsvDefinition csvdef))
+                return;
             int newLanguageId;
             if (currentLanguageId == CsvLanguageId.Value)
             {
@@ -540,13 +542,20 @@ public static void UpdateCSVChanges(CsvDefinition csvdef, bool saveini)
             }
         }
 
-        public static CsvDefinition GetCurrentCsvDef()
+        /// <summary>
+        /// If this returns false, csvdef is null.<br></br>
+        /// Otherwise, csvdef is the CsvDefinition for the current file.
+        /// </summary>
+        public static bool TryGetCurrentCsvDef(out CsvDefinition csvdef)
         {
+            csvdef = null;
+            if (!Helper.TryGetLengthAsInt(PluginBase.CurrentScintillaGateway, true, out _))
+                return false;
             // Notepad++ switc to a different file tab
             INotepadPPGateway notepad = new NotepadPPGateway();
             string filename = notepad.GetCurrentFilePath();
 
-            return FileCsvDef.TryGetValue(filename, out CsvDefinition result) ? result : null;
+            return FileCsvDef.TryGetValue(filename, out csvdef);
         }
 
         public static bool CheckValidCsvDef(CsvDefinition csvdef, string errmsg)
@@ -605,7 +614,8 @@ internal static void DoAboutForm()
         internal static void convertData()
         {
             // get dictionary
-            CsvDefinition csvdef = GetCurrentCsvDef();
+            if (!TryGetCurrentCsvDef(out CsvDefinition csvdef))
+                return;
 
             // check if valid csv metadata
             if (CheckValidCsvDef(csvdef, "convert data"))
@@ -647,7 +657,8 @@ internal static void convertData()
         internal static void generateMetaData()
         {
             // get dictionary
-            CsvDefinition csvdef = GetCurrentCsvDef();
+            if (!TryGetCurrentCsvDef(out CsvDefinition csvdef))
+                return;
 
             // check if valid csv metadata
             if (CheckValidCsvDef(csvdef, "generate script"))
@@ -692,7 +703,8 @@ internal static void generateMetaData()
         internal static void AnalyseDataReport()
         {
             // get dictionary
-            CsvDefinition csvdef = GetCurrentCsvDef();
+            if (!TryGetCurrentCsvDef(out CsvDefinition csvdef))
+                return;
 
             // check if valid csv metadata
             if (CheckValidCsvDef(csvdef, "run Analyze Data Report"))
@@ -705,7 +717,8 @@ internal static void AnalyseDataReport()
         internal static void CountUniqueValues()
         {
             // get dictionary
-            CsvDefinition csvdef = GetCurrentCsvDef();
+            if (!TryGetCurrentCsvDef(out CsvDefinition csvdef))
+                return;
 
             // check if valid csv metadata
             if (CheckValidCsvDef(csvdef, "count unique values"))
diff --git a/CSVLintNppPlugin/PluginInfrastructure/IScintillaGateway.cs b/CSVLintNppPlugin/PluginInfrastructure/IScintillaGateway.cs
index 9274bd1..31b6653 100644
--- a/CSVLintNppPlugin/PluginInfrastructure/IScintillaGateway.cs
+++ b/CSVLintNppPlugin/PluginInfrastructure/IScintillaGateway.cs
@@ -55,7 +55,7 @@ public interface IScintillaGateway
         void ClearDocumentStyle();
 
         /// <summary>Returns the number of bytes in the document. (Scintilla feature 2006)</summary>
-        int GetLength();
+        long GetLength();
 
         /// <summary>Returns the character byte at the position. (Scintilla feature 2007)</summary>
         int GetCharAt(int pos);
diff --git a/CSVLintNppPlugin/PluginInfrastructure/ScintillaGateway.cs b/CSVLintNppPlugin/PluginInfrastructure/ScintillaGateway.cs
index a509173..6970e5f 100644
--- a/CSVLintNppPlugin/PluginInfrastructure/ScintillaGateway.cs
+++ b/CSVLintNppPlugin/PluginInfrastructure/ScintillaGateway.cs
@@ -144,9 +144,9 @@ public void ClearDocumentStyle()
         }
 
         /// <summary>Returns the number of bytes in the document. (Scintilla feature 2006)</summary>
-        public int GetLength()
+        public long GetLength()
         {
-            return (int)Win32.SendMessage(scintilla, SciMsg.SCI_GETLENGTH, (IntPtr) Unused, (IntPtr) Unused);
+            return (long)Win32.SendMessage(scintilla, SciMsg.SCI_GETLENGTH, (IntPtr) Unused, (IntPtr) Unused);
         }
 
         /// <summary>Returns the character byte at the position. (Scintilla feature 2007)</summary>
diff --git a/CSVLintNppPlugin/PluginInfrastructure/ScintillaStreams.cs b/CSVLintNppPlugin/PluginInfrastructure/ScintillaStreams.cs
index 11d4617..b48e64e 100644
--- a/CSVLintNppPlugin/PluginInfrastructure/ScintillaStreams.cs
+++ b/CSVLintNppPlugin/PluginInfrastructure/ScintillaStreams.cs
@@ -9,24 +9,32 @@
     public class ScintillaStreams
     {
         /// <summary>
-        /// Reads the whole document as a text stream, trying to use the right encoding
+        /// If the current document has more than <see cref="int.MaxValue"/> bytes:<br></br>
+        /// * throw up a MessageBox as described in <see cref="Helper.TryGetLengthAsInt(IScintillaGateway, out int)"/><br></br>
+        /// * return false and reader is null<br></br>
+        /// Otherwise, return true, and reader is a StreamReader tha treads the whole document as a text stream, trying to use the right encoding
         /// </summary>
-        public static StreamReader StreamAllText()
+        public static bool TryStreamAllText(out StreamReader reader, bool notifyUser = true)
         {
+            reader = null;
             var doc = PluginBase.CurrentScintillaGateway;
+            if (!Helper.TryGetLengthAsInt(doc, notifyUser, out _))
+                return false;
             var codepage = doc.GetCodePage();
             var encoding = codepage == (int)SciMsg.SC_CP_UTF8 ? Encoding.UTF8 : Encoding.Default;
-            return new StreamReader(StreamAllRawText(), encoding);
+            reader = new StreamReader(StreamAllRawText(), encoding);
+            return true;
         }
 
         /// <summary>
-        /// Reads the whole document as a byte stream.
-        /// Will likely throw exceptions if the document is edited while the stream is open.
+        /// Reads the whole document as a byte stream.<br></br>
+        /// Will likely throw exceptions if the document is edited while the stream is open.<br></br>
+        /// Will also throw an exception if the document has more than <see cref="int.MaxValue"/> characters.
         /// </summary>
         public static Stream StreamAllRawText()
         {
             var doc = PluginBase.CurrentScintillaGateway;
-            var length = doc.GetLength();
+            var length = (int)doc.GetLength();
 
             // When editing a document Scintilla divides it into two - one before the cursor and one after, calling the break point the "gap"
             int gap = doc.GetGapPosition();
diff --git a/CSVLintNppPlugin/Tools/Helper.cs b/CSVLintNppPlugin/Tools/Helper.cs
index e1513af..1db63d6 100644
--- a/CSVLintNppPlugin/Tools/Helper.cs
+++ b/CSVLintNppPlugin/Tools/Helper.cs
@@ -2,11 +2,13 @@
 // CsvDefinition
 // Helper functions and methods
 // -------------------------------------
+using Kbg.NppPluginNET.PluginInfrastructure;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+using System.Windows.Forms;
 
 namespace CSVLint.Tools
 {
@@ -25,5 +27,34 @@ public static void Increase<T>(this Dictionary<T, int> counts, T c)
             else
                 counts[c]++;
         }
+
+        /// <summary>Tell the user the first time they try to use a plugin command on a too-long file, but let them turn off such notifications</summary>
+        private static bool notifyUserIfFileTooLong = true;
+
+        /// <summary>
+        /// Let <c>longLen</c> be the number of bytes in the document managed by scintilla<br></br>
+        /// If <c>longLen</c> is less than <see cref="int.MaxValue"/>, returns true and sets <c>length = longLen</c>.<br></br>
+        /// Otherwise, <c>length = -1</c> and returns false, and if (<see cref="notifyUserIfFileTooLong"/> && notifyUser), throws up a MessageBox warning the user that the file is too long.
+        /// </summary>
+        public static bool TryGetLengthAsInt(IScintillaGateway scintilla, bool notifyUser, out int length)
+        {
+            long longLen = scintilla.GetLength();
+            if (longLen >= 0 && longLen <= int.MaxValue)
+            {
+                length = (int)longLen;
+                return true;
+            }
+            length = -1;
+            if (notifyUser && notifyUserIfFileTooLong)
+            {
+                notifyUserIfFileTooLong = MessageBox.Show(
+                    $"This plugin command cannot be performed on this document, because the document has more than {int.MaxValue} characters.\r\n" +
+                        $"Do you want to stop showing these messages for too-long documents?",
+                    "Document too long for this command",
+                    MessageBoxButtons.YesNo, MessageBoxIcon.Warning
+                ) == DialogResult.No;
+            }
+            return false;
+        }
     }
 }
diff --git a/CSVLintNppPlugin/bin/Release-x64/CSVLint.dll b/CSVLintNppPlugin/bin/Release-x64/CSVLint.dll
index 641a9f3..a5f00b2 100644
Binary files a/CSVLintNppPlugin/bin/Release-x64/CSVLint.dll and b/CSVLintNppPlugin/bin/Release-x64/CSVLint.dll differ
diff --git a/CSVLintNppPlugin/bin/Release/CSVLint.dll b/CSVLintNppPlugin/bin/Release/CSVLint.dll
index c647b53..166ef38 100644
Binary files a/CSVLintNppPlugin/bin/Release/CSVLint.dll and b/CSVLintNppPlugin/bin/Release/CSVLint.dll differ