SixLabors/ImageSharp · error · ArgumentException

The iptc value exceeds the limit of

Error message

The iptc value exceeds the limit of {maxLength} bytes for the tag {this.Tag}

What it means

IPTC records cap each field at a fixed byte length (per tag). The IptcValue constructor truncates the string to maxLength characters, but the encoded bytes can still exceed the limit, in which case it throws ArgumentException rather than silently writing a malformed record.

Solutions

1. Shorten the value so it fits the tag's byte limit under the chosen encoding
2. Use a single-byte encoding such as Latin-1 (ISO-8859-1) for the IptcProfile so more characters fit per byte
3. Truncate the value yourself by encoding incrementally and cutting at a character boundary within maxLength
4. Catch ArgumentException and skip or log the oversized field when writing metadata in bulk

Example fix

// before
new IptcValue(Encoding.UTF8, IptcTag.Caption, veryLongUnicodeCaption, true);
// after
profile.Update(new IptcValue(Encoding.Latin1, IptcTag.Caption, veryLongUnicodeCaption[..80], true));

int max = 64; // per-tag limit
byte[] bytes = Encoding.Latin1.GetBytes(value);
if (bytes.Length > max) value = Encoding.Latin1.GetString(bytes[..max]);

static bool FitsTag(string v, Encoding enc, int maxLength) => enc.GetByteCount(v) <= maxLength;

try { profile.Update(new IptcValue(encoding, tag, value, strict: true)); } catch (ArgumentException ex) { log.Warn(ex, $"IPTC value too long for {tag}"); }

When it happens

Trigger: Constructing new IptcValue(encoding, tag, value, strict) where encoding.GetBytes(value) produces more bytes than the tag's maxLength even after string-level truncation — typical with multi-byte encodings (UTF-8/UTF-16) where characters cost more than one byte.

Common situations: Long captions or keywords written with UTF-8 non-ASCII characters (accents, CJK) exceeding e.g. a 64-byte limit; using an encoding wider than the record expects.

Understand the failure class

Background: payload too large / request exceeds maximum size: why libraries cap bytes and how to fix oversize payloads — this error's family across 50 libraries.

Related errors

• Iptc profile size exceeds limit of
• CICP matrix coefficients other than Identity are not…
• Iptc tag is not a time or date type.
• No encoder was found for extension
• Image is too large to encode in EXR format.

AI-assisted analysis of SixLabors/ImageSharp@59ce6af6fc (2026-09-13). Data as JSON: /api/errors/58b60ad5c7270af6. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/Metadata/Profiles/IPTC/IptcValue.cs:109

        set
        {
            if (string.IsNullOrEmpty(value))
            {
                this.data = [];
            }
            else
            {
                int maxLength = this.Tag.MaxLength();
                byte[] valueBytes;
                if (this.Strict && value.Length > maxLength)
                {
                    string cappedValue = value[..maxLength];
                    valueBytes = this.encoding.GetBytes(cappedValue);

                    // It is still possible that the bytes of the string exceed the limit.
                    if (valueBytes.Length > maxLength)
                    {
                        throw new ArgumentException($"The iptc value exceeds the limit of {maxLength} bytes for the tag {this.Tag}");
                    }
                }
                else
                {
                    valueBytes = this.encoding.GetBytes(value);
                }

                this.data = valueBytes;
            }
        }
    }

    /// <summary>
    /// Gets the length of the value.
    /// </summary>
    public int Length => this.data.Length;

    /// <inheritdoc/>

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